Discussion in 'Oil and Lube Systems' started by Maniacmechanic1, Mar 10, 2019.
I found a few articles on Racing Oils for Drag race Use.
Not for typical street cars .
What is the best oil to use in my performance engine?
This is a sticky subject and there are lots of opinions and theories on it which can all be in-part true or not. It just depends on how you look at it and what best suits your needs. Here's what I was told by an old friend of mine from Redwood Oil, who was an refining engineer, so he should know what he's talking about. There are basically 3 kinds of oils, ash based, paraffin based and synthetic.
Ash based oils are what I prefer. They are commonly Valvoline, Kendall, Castrol and a few other's. Paraffin based oils are "wax" based and you have probably seen old, neglected engines where you take-off a valve cover and it's literally caked with crud inside with this light weight, dry substance stuck to everything and clogging everything up. That is paraffin wax from the oil. You'll hear old time engine builder's call engines like that, "Pennzoil engines". Don't get me wrong, there's nothing wrong with paraffin based oils (or Pennzoil) as far as protection goes, it's only when you leave that kind of oil in there too long that it starts coating the insides of everything with wax, and just like when making candles the old fashioned way, by dipping a piece of string into hot wax over and over again, it builds-up on the string until you have a candle. This is exactly what goes-on inside your engine every time it heats up and cools down if you don't keep the paraffin based oils fresh and clean.
Oil weights are another story. We used to mainly use straight weights, such as 30 wt. for standard engines and 40 wt. and 50 wt. for racing engines. This was due to whatever the inside clearances were and temperatures that the engines were going to be run at. A racing engine is usually set-up loose, (wider clearances), than a basic street engine, and most racing engines are run in warm, Summer weather, which would require a thicker oil to take-up the clearances to keep the engine protected. A tighter engine, such as a stock engine, would require thinner oil such as 30 wt.
These days, with multi viscosity oils, you get better protection BUT there is a real misconception on this. 10W-40 oil is not 10 weight when it's cold and 40 wt when it's hot like a lot of people think multi viscosity oils do. The "w" in the weight listing stands for "winter". It's supposed to indicate how the oil will flow during cold winter months, but that to is subject to circumstances because a "winter" in Arizona is a hell of a lot different than a "winter" is on Wisconsin. Wisconsin might be 0 degrees or colder in Winter, where in Arizona you might wake-up to 80 degree winter mornings. Oils are thicker when they are cold and thinner when they are hot. The best way I can say to understand this is to think of the "w" as meaning the "cold weight" of the oil, so think of a 10w-40 oil as being a 10 weight oil "base" which will indicate how the oil will flow in cold temperatures. Along the same lines, think of a 20w-50 oil as having a 20 wt cold base flow rating, so it'll be a little thicker when cold than a 10w-40 oil would be. That's about the easiest way I can think of to explain it.
So think of a 10W-40 oil as meaning that the oil is similar in flow to a 10 weight based oil, but when it's hot, it will have the "viscosity" protection of 40 weight oil. It does NOT turn into 40 weight oil like so many people think multi viscosity oils do. They are called "multi viscosity" for a reason, not "multi weight" oil. It isn't meat gravy! It doesn't get thicker when it heats up. Don't believe me? That's an easy one to prove. Check your dip stick when your engine is cold. The oil stays on the dip stick as normal because it is at it's normal, thicker cold "weight". Now check it when the engine is hot, the oil will run off that dip stick like it was thinner than water! Like I said, it ain't gravy and it does not thicken when it gets hot.
20w-50 oil is the same way. Think of it as having the cold flow of a 20 weight oil, and the protection, or "viscosity", of 50 weight oil when it gets to running temperature. This is because the molecules in the oil are kind of like tiny little springs. When they heat-up, they expand, and when they are cold, they contract... in simple terms. This expansion and contraction does not thicken the oil when it gets hot. It still thins-out like any oil does. It just means that a 20w-50 oil will be a little thicker when cold than something like a 10w-30 or a 10w-40 oil would be. This means a 10w-30 or a 10w-40 oil will get to the places it needs to go quicker than a 20w-50 or a straight 30 wt oil will because thinner oil is easier to push and it can get into the tighter clearance places easier than a thicker oil can. It's easier to drink a soda pop through a straw than it is a milkshake. It's kind of along those same lines.
Now, what's a good weight to run in your engine? Most modern car engines have very tight clearances and need thinner oils so the oil can get where it needs to go to do it's job as fast as possible. Thick oil has a hard time getting in tight places or getting where it needs to go until it warms-up and thins out. That's why we always warm-up our performance engines before we started driving or putting any loads on the engine. This makes sure the oil is warmed-up, thinned-down, and has had time to get where it needs to go to start protecting the internals of the engine before loads or RPM is given to it.
Thinner oils have less drag on the oil pump and drive gears, which equates to less parasitic power loss. But again, too thin of oil can also mean less protection under high loads and high heat, so there is no one perfect answer. The problem with thin oil is that most oil and advertising is geared towards the East coast where it is very cold in the Winter so thinner oil is more suited. The West coast almost never gets that cold, so the oils we use out here need to be thicker with higher viscosity numbers. I would never recommend 0w-30 or 5W-30 oil in ANY "American" performance engine, let alone any normal street cars in warm weather. That stuff is like water and can't take the kind of heat and loads of an American performance engine. Import engines use tighter clearances and have different designs than older "muscle car era" American engines have, so when it comes to oil, we aren't talking apples to apples, it's more like apples to oranges. This can go on and on, so I'll try to keep it brief. If you look in a Valvoline catalog under oil recommendations, they recommend 30Wt. in trucks that drive in weather over 80 degrees. Well, that is pretty normal weather for the West coast.
The nitty gritty of oils: Mineral oil is refined, and the refining process is pretty good, but not perfect. Here's how my friend from Redwood Oil explained it to me so it was easy to understand: Crude oil has everything in it, from gasoline to diesel to all of the weights of oil, and each part is processed out of the whole crude oil. Once the oil has been refined out of the crude, also known as "heavies", what they do to get the different weights is by separating the different sizes of molecules that make-up the thickness of the oil.
Oil molecules are like little ball bearings that let metal to metal parts glide on them between a certain clearance. Thin oil has small ball bearing like molecules. Thicker oils have larger molecules. Picture a bag of marbles, where you have 100 individual marbles. Now instead of having all of the marbles the exact same size, imagine about 80% of the marbles being 1" in diameter and 10% being 3/4" in size, while the remaining 10% being 1 1/8" in diameter. Now lay out all of the marbles on a flat surface and lay a piece of plywood over the top of it. What is the board going to be riding on? The small percentage of the largest 1 1/8" marbles that are scattered out under the board. This doesn't provide an even load for the plywood to ride on. The load bearing area is sparse and is only on those large 1 1/8" marbles. Well, that won't make the board very stable and it won't be riding on the majority of the 1" marbles like it is supposed to be doing until the biggest marbles have been made smaller in size so they can ALL carry the load smoothly and glide the board across the surface of the ground.
This is very much like refined oil. Refined oil has a high percentage of the correct size molecules, BUT, there is also a percentage of carry-over sizes that are smaller or larger in size as well. They can't refine it perfectly. Your engine bearings are like that piece of plywood, not riding smoothly on ALL of the marbles, only on the largest ones which makes the load surfaces uneven and smaller.
Now imagine the same piece of plywood with the same 100 marbles, only this time, they are ALL exactly 1" in size, thus dispersing the load over the entire surface of the plywood and the floor. That would be the ideal situation. This is very much like synthetic oil molecules, where the molecules are not refined and sorted-out by size but rather are MADE synthetically to a very specific size which carries more of a load and disperses the load over a greater surface area. That is why synthetic oils work so much better than refined oils. The only problem I have ever found with synthetic oils is if you don't have an oil leak with regular oil, you probably will once you go to synthetic. That stuff just has a way of finding its way out of your engine.
So, what do we recommend as far as oil goes? I like using 15w-40 in most of the engines I build and 20W-50 in engines that are in hotter climates, such as places like Texas or Arizona. Be them synthetic or ash based, it really doesn't matter much. I rarely use paraffin based oils and rarely use anything thinner than what I listed.
Jan 16, 2015 10:29 am
Picking a Racing Oil
How do racing oils differ from everyday motor oils? You might think all racing oils are synthetics, but they are not. Some use conventional mineral base oils, others use PAO and ester synthetics, and some are a blend of conventional and synthetic oils. Some racing oil suppliers refine their own oil while others are blenders who buy base stocks from other oil companies and mix in their own additive package. It doesn’t really matter which way a racing oil is created as long as it meets the criteria for which it was designed.
Racing oils are formulated for hard use, high temperature operation. This requires a high quality base stock with an additive package that provides superior wear resistance and oxidation resistance compared to an everyday motor oil. Base oils make up 70% to 90% of the liquid that’s in a bottle of oil. The rest is various additives. A high quality base oil usually requires fewer additives to achieve good performance, while less quality oils need a better additive package. The bottom line is that two different racing oils formulated using different base stocks and additive packages can often meet the same performance criteria.
When choosing a racing oil, therefore, comparing apples to apples can be difficult because of the different base stocks and additives that are used. Most oil companies will only hint at what’s in their product, preferring to keep their exact formula a proprietary secret. They may make certain claims as to how the oil performs or how much anti-wear additive it contains, but trying to compare one motor oil directly to another can be very confusing. Motor oils with the same viscosity rating can have very different additive packages and very different performance characteristics. So the best advice we can offer when it comes to choosing a particular brand of motor oil is to go with a brand that has a good reputation with the racing community. It doesn’t matter if the product is made by a big oil company with a big promotional ad budget or blended by a small supplier who relies on word-of-mouth advertising.
That said, let’s take a closer look at what goes into a racing oil and how that may affect the way you choose to build an engine.
All About That Base
Base oils are rated according to their “Viscosity Index” (VI) or pour point, how many “saturates” (paraffin and naphthenes) they contain, sulfur content, volatility, flash point, oxidation stability and other factors. Petroleum engineers have developed test procedures and a rating system for grading various base stocks.
• Group I oils are the easiest to refine and least expensive lubricants. They also contain lower levels of saturates (less than 90), higher levels of sulfur (over 500 ppm) and usually have a viscosity index rating of less than 100. Group I mineral oils have long been used in straight weight and multi-viscosity everyday motor oils, and are often blended with Group II or III oils in some multi-viscosity oils. But Group I base oils are generally not used in racing oils.
• Group II base oils are higher quality lubricants that are commonly used in today’s multi-viscosity oils. They contain a higher percentage of saturates (greater than 90), lower levels of sulfur (less than 500 ppm), and have a viscosity index rating over 100.
• Group III base oils have a viscosity index rating usually over 120, and include many synthetic oils.
• Group IV base oils are pure PAO synthetics and are the highest quality generally used in automotive applications.
Which group a base oil ends up in depends on how it was refined or made, and how it performs. Mineral base oils are refined from crude oil (paraffinic, naphthenic and aromatic) while synthetic oils undergo additional refining and may be made from crude oil or natural gas. Synthetic oils fall into several subcategories: PAOs (polyalphaoefin), diesters, polyol esters and PAGs (polyalkylene glycols).
This is a lot of chemistry you really don’t need to know to choose a racing oil. But it’s helpful to understand what some of these terms mean and how marketing people tend to misuse them in promoting various high performance lubricants.
The general consensus is that synthetic oil is better than conventional mineral oil. Most synthetic oils do have inherent advantages over conventional oils because synthetic oils undergo additional refining, distillation and purification that results in a very high quality and consistent base stock. Synthetic oils generally pour more easily at lower temperatures, resist oxidation better at higher temperatures, stay cleaner longer (extended drain intervals) and superior lubrication and wear protection. One oil supplier says the molecules in synthetic oils are more consistent in size. This allows a synthetic oil to provide a higher film strength. Translated, this means although a synthetic oil is often thinner than a conventional mineral oil, it clings better to bearing surfaces under load.
Synthetic oils also have lower volatility, which reduces evaporation losses when the oil is hot. Synthetic oil is also more sheer stable, which means its viscosity characteristics are more predictable and consistent, and undergo less change over time than a conventional mineral oil. Some synthetic oils also provide better air release, reducing the risk of aeration and bubbles being trapped in the oil when it is being whipped into foam by a spinning crankshaft.
High-quality conventional mineral oils can perform well in many racing applications with the right additive package, but for the most demanding applications many oil experts say a full synthetic will usually provide the best protection and performance.
Oil is relatively cheap, even the most expensive full synthetic racing oils when you compare the cost of the oil to all of the machine work and parts that have gone into a high performance engine. Why scrimp on oil quality and risk an engine failure if a premium quality racing oil can provide extra protection?
The Antidote to Wear
One of the key components in any racing oil is anti-wear additive. Typically this includes ZDDP (zinc dialkyl dithiophosphate) as well as other ingredients such as moly. ZDDP is a mixture of zinc and phosphorus, although many people simply refer to it as “zinc”. The exact proportions of zinc and phosphorus in ZDDP can vary somewhat but generally there is slightly more phosphorus than zinc. Under extreme pressure, these compounds provide a protective barrier that prevents metal-to-metal contact and wear.
Everyday motor oils for passenger car and light truck applications that meet current API (American Petroleum Institute) “SN” specifications and/or ILSAC GF-5 specifications contain reduced levels of ZDDP (less than 800 PPM). Phosphorus is great stuff for preventing wear, but it can also contaminate catalytic converters and oxygen sensors, reducing service life – especially if the engine is burning oil due to worn valve guide seals or piston rings. The amount of ZDDP in current motor oils was reduced from earlier levels of 1200 PPM because most late model engines have roller cams or overhead cams. Reduced friction in the valvetrain means these engines don’t need as much ZDDP for wear protection. But that’s NOT the case with performance engines or older engines with flat tappet cams. They need higher levels of anti-wear protection.
Most people assume that one of the hallmarks of a racing oil is that it contains at least 1500 PPM of ZDDP, or even more (some contain as much as 2000 PPM of ZDDP). That’s generally true, but there are performance lubricants on the market that contain as little as 1100 PPM of ZDDP thanks to the higher quality base oils in the product and other additives (such as moly).
The exact amount of ZDDP in a racing oil doesn’t matter, nor does more always mean better as long as there is enough to protect the valvetrain components against wear. Some engines need more, some can get by with less. Extremely high RPMs and extremely stiff valve springs can place tremendous loads on the cam and lifters, so foe these applications a racing oil that contains extra ZDDP or other anti-wear additives is usually a must to prevent cam or valvetrain failure.
Taking it to the Streets
Street performance oils are a subcategory within racing oils that are formulated for the typical vintage muscle car or street/strip machine. Some of these oils are not API-rated, although they usually meet all of the other performance criteria for a modern motor oil. The main difference is that they contain 1200 PPM or more ZDDP to protect flat tappet cams and lifters against premature wear. Since most of these vehicles are not equipped with oxygen sensors or catalytic converters, phosphorus contamination is not an issue. Such products are usually NOT recommended for late model vehicles that have electronic engine controls (O2 sensors) and catalytic converters.
For more demanding racing applications, specially formulated racing oils with the highest quality synthetic base stocks may be required to provide the utmost protection and lubrication. Some racing oils are formulated for engines that are running alcohol, or for blown, turbocharged or nitrous applications. The best advice here is to follow the application recommendations of the oil supplier. They know their individual additive packages and formulations and can help you choose a product that is right for the application.
Most late-model passenger car and light truck engines are factory-filled with 5W-20 or 5W-30 multi-viscosity oil, with some European makes specifying 0W-40 or even 0W-20 for Japanese hybrids like the Toyota Prius. Thinner oils make cold starting easier and improve fuel economy. Thinner oils also flow more quickly following a cold-start to speed lubrication to the bearings, cam and upper valvetrain. For older pushrod engines, 10W-30 is still the most popular viscosity. But for racing applications, the viscosity you choose can vary depending on engine bearing clearances, ambient temperatures, engine RPMs and customer preferences.
Racing oil viscosities run the gambit from newly introduced 0W-50 and 0W-60 multi-viscosity synthetic oils to 0W-30, 0W-40, 5W-20, 5W-30, 5W-40, 10W-30, 10W-40, 15W-40, 15W-50 and 20W-50 multi-viscosity oils, to various straight weight oils including 30, 40, 50 and 70.
Each oil is formulated for a particular niche, but the oil companies usually won’t tell you which oil they recommend. They leave that up to the engine builder and the end user to decide.
Traditional old school engine builders and racers like looser bearing clearances, lots of oil pressure and a relatively thick oil such as 15W-40, 15W-50 or a straight 40 or 50 weight oil in the crankcase. A heavier viscosity oil helps cushion the bearings and won’t drain off as quickly as a thinner viscosity oil if the engine loses oil pressure momentarily.
Others say they can gain additional horsepower running tighter bearing clearances, less oil pressure and using a lower viscosity racing oil such as a 0W-20, 0W-30 or 5W-20. Thinner oils require tighter bearing clearances to maintain oil pressure, but they also reduce friction to free up more horsepower. What’s more, they can reduce the load on the oil pump which also frees up more power.
One of the most common misconceptions with thinner multi-viscosity oils is that might be too thin to provide adequate lubrication in a high performance engine at high temperature. The numbers on a multi-viscosity rating tell a different story. The first number is the viscosity when the engine is cold. The lower the number, the thinner the oil and the easier it flows. The second number is the viscosity when the oil reaches operating temperature. Consequently, once the oil is hot, a 0W-40 oil flows and lubricates the same as a straight 40 weight oil. This transformation occurs thanks to the rubber-like “viscosity improvers” that are blended with the base oil to give it its multi-faceted personality.
For higher temperature applications (such as endurance racing in hot climates), a heavier multi-viscosity oil is usually recommended (something like a 15W-50 oil). Recently, however, several oil companies have introduced 0W-50 and 0W-60 multi-viscosity racing oils for rally racing and off-road racing. The broader viscosity provides good cold lubrication for overhead cams and turbocharger shaft bearings, while the higher hot viscosity rating keeps everything well lubed at peak operating temperatures.
For a really demanding application such as Top Fuel drag racing, a heavy straight weight oil (usually 70) is required because of the extreme loads on the bearings and the fuel blowby that ends up in the crankcase. And the oil is usually so diluted after each run that it usually has to be changed.
How often should racing oil be changed? It depends on the application and how far the end user wants to push his oil. If the oil looks dirty and/or smells bad, it needs to be changed. Dirt track racing and off-road racing are very dirty environments, so changing after every weekend of racing is a common practice. A drag racer, on the other hand, might go all season on the same batch of oil unless he sees a lot of fuel dilution in the crankcase or oil discoloration.
The bottom line is there is no pat answer as to how often racing oil should be changed. Oil life depends on the quality of the oil, the additives in the oil, how hot the oil gets and how much contamination ends up in the crankcase. Obviously, if an engine has experienced a major bearing, piston or rod failure, the old oil has to go and everything has to be thoroughly cleaned to remove any debris that could cause problems later on. This includes flushing out all the oil galleys, external oil lines, oil cooler and/or reserve tank.
Racing Oil vs. Street Oil: Know the Differences
By John Baechtel January 15, 2013
The difference between racing oil and street oil is largely characterized by the base oil chemistry and various additive packages specified by engine manufacturers. Additive packages contribute multiple levels of lubrication efficiency and protection — including anti-wear, friction reduction, rust and corrosion resistance and detergent and dispersant qualities — that help keep engine internals clean and functioning properly.
Effects of racing on oil
Here’s what racing oil looks like after 500 miles in a NASCAR engine. On the right is fresh 20W-50 synthetic racing oil, and on the left is oil pulled from Mark Martin’s Ford following his victory at Fontana in 1998. The discoloration is the result of oxidation, which is caused by heat, soot and other combustion carbon byproducts that blow by the rings. Those engines produced about 700 horsepower. Today’s Cup engines run 5W-20 synthetic oil and make close to 900 horsepower.
“Just like cams are ground differently for street driving versus superspeedway racing, high-performance street oils are formulated differently than racing oils — due to the subtle differences in each application,” explains Lake Speed, Jr., a certified lubrication specialist at Driven Racing Oil. “The little details make a big difference.”
“Racing oil is more heavily fortified with additive systems to give the performance to protect the engine,” sums up Mark Negast, technical director at Lucas Oil Products. “Still the same additive systems, just higher concentrations.”
“Racing oils are formulated without regard to emissions equipment life,” adds Chris Barker, technical services manager at Royal Purple.
Today’s late-model cars are well served by contemporary, over-the-counter motor oils. These formulas evolved with complementary qualities engineered to accommodate a broad range of operating conditions, including catalytic converter preservation and long-term emissions compliance. But many contemporary motor oils have reduced anti-wear qualities as late-model engines enjoy fewer critical high-friction challenges. That leaves early performance engines or modified racing engines equipped with flat-tappet cams and high valve-spring pressures at risk with current motor oils.
“Anti-wear additives come in many different formulations with each major additive supplier offering multiple versions of differing efficacy and molecular structure,” says Barker.
Different additive packages
Oil suppliers incorporate additive packages they deem necessary to meet the requirements of specific applications. To maintain consistency throughout the industry, the American Petroleum Institute (API) — working in concert with major automakers through the trade group, International Lubricants Standardization and Approval Committee (ILSAC) — recommend voluntary minimum performance standards and chemistry restrictions. All API and ILSAC licensed oils are suitable for any production passenger car or light truck with a stock engine. Those formulas, however, may not provide enough protection for modified performance engines, particularly during engine startup and break-in.
Zinc, along with phosphorus, sulfur and sometimes other elements, comprise these anti-wear additives. The most common are a family of compounds generally referred to as ZDDP, or ZDP, which stands for Zinc Dialkyl Dithiophosphates. In engine slang, ZDDP may be simply but incorrectly referred to as “zinc.”
By itself, the element zinc provides absolutely no benefit in engine oil. The chemical compounds containing the additional elements actually provide the sacrificial phosphate layer that, under high pressure and temperature, protects highly loaded sliding surfaces against wear damage.
“There are many different ZDDP chemistries with varying levels of quality and performance,” adds Barker.
Understanding anti-wear additives
Matching viscosity and clearances is critical.
— Lake Speed, Jr.
All engine oils still contain anti-wear additives, though in lesser amounts than previous generations, due to concerns for emissions equipment life. The chemistry restrictions set by API originally targeted only phosphorus — which can be harmful to catalytic converters — and currently stand at 800ppm (parts per million). Phosphorus is typically only found in anti-wear additives, so a restriction on total phosphorus puts a restriction on the total additive. Along with phosphorus, the chemistry restrictions also address “ash” content, which is determined by weighing the residual left after a measured amount of oil is boiled and burned away. The various additives contained in engine oil, including anti-wear additives, contribute to total ash content.
This type of wear and damage can occur when the wrong oil formula is used in an engine.
The decrease in anti-wear additives coincided with steady improvements to additive chemistry and oil formulation across the board. Though modern engine platforms have incorporated lower-friction components to reduce the need for anti-wear additives, new production engines also have a much greater power-to-displacement ratio and a life expectancy in excess of 200,000 miles. Engines from the 1970s and early 1980s during the “high-zinc era” were lucky to achieve 100,000 miles before a rebuild was required. With every new API oil specification, the requirements for wear protection, corrosion protection, and cleanliness increased, in spite of an overall reduction in anti-wear additive.
Some oil companies offer API-licensed oils for production engines as well as formulas for performance street engines. Look for the API certification label when shopping for formulas for production engines.
ZDDP can be described as a polar molecule whose protective qualities are activated by heat and load. Different families of ZDDP are classified by their burn or activation rate and percentage of ZDDP in relation to detergents, rust inhibitors and other components.
“ZDDP additives with faster activation rates are more suitable for racing and high performance street engines with challenging friction characteristics, such as flat tappets or new engines undergoing break-in,” says Speed.
Performance oil manufacturers address anti-wear concerns each in their own way. Driven’s racing and street performance oils are characterized by increased levels of ZDDP and dramatic reductions in detergent levels to achieve high anti-wear characteristics. In part, this strategy is based on projected frequency of filter changes and drain intervals typical of street performance engines with infrequent use.
ZDDP and detergents
“For higher rpm and horsepower, you might see lower concentrations of calcium,” echoes Negast. “Typically what happens is the calcium competes for area surface with the zinc and phosphorus. In NASCAR and IndyCar, you’ll see a reduction in calcium detergents because they’re not necessary. In NHRA, you don’t need detergent at all, just wear protection.”
However, Royal Purple points to SAE papers showing that certain families of ZDDPs and detergents actually perform better when combined.
Forrest Lucas of Lucas Oil works on new formulas in the lab.
“An engine oil with little to no detergency and with excessive anti-wear additives will result in excessive engine deposits,” says Barker.
While the different companies offer a wide range of high quality lubricants with chemistries developed according to their individual philosophies, the following criteria should be considered when choosing the best oil for specific applications: engine speed, engine load, operating temperature, engine content (flat tappet, valve-spring pressure, etc.), operating clearances and operating environment.
High piston speeds in race engines also affect the engine builder’s choice of oil. Cylinder wall and piston skirt lubrication are normally covered by splash oil coming off the rod bearings and the camshaft. But as piston speed exceeds 5,000 feet per minute, the hydrodynamic oil film between the piston skirt and the cylinder wall begins to lose effectiveness, which will cause pistons to scuff. The minimal fog of lubricant in the crankcase has no time to attach itself to the cylinder wall. The problem is exacerbated in dry-sump applications that remove oil from the pan very quickly. Also, some engine-block designs isolate the cam tunnel to eliminate cam and lifter oil from dripping on the crankshaft. All these racing modifications reduce the amount of oil being splashed on the cylinder walls. Racing oils with properly specified additives and correctly matched viscosity for the application and operating clearances involved can help provide protection where pin oilers are not available to help splash lube the walls.
‘Lubricity’ in race and street oils
One lingering myth about racing oil is that it has more “lubricity” than street oil. Simply not true. The additive packages required for production engines do not affect the oil’s lubricity.
“All engine oils for automotive use want as much lubricity as possible,” explains Barker. “Oil companies or automakers won’t specify fewer lubricity agents unless there’s a downside. The differences between race and street oil all comes down to the chemistry restrictions associated with the API license.”
Oil is also used as a coolant. Many new production and racing engines use oil squirters to cool the piston from underneath.
Cooling is another vital and often unrecognized function performed by engine oil. It encourages component longevity, so engine builders spray oil on the valve springs, camshafts and the bottom of the piston crowns to keep them cool. These components operate in a severe temperature environment and maximum oil performance is required to support them. Conventional mineral oils are comfortable up to about 260°F while the superior thermal qualities and shear resistance of synthetic oils still provides protection even above 300°F without viscosity breakdown.
When choosing engine oil, picking the appropriate viscosity grade is extremely important. Automotive engines are typically tolerant of viscosity, but go too far to the light or heavy ends of the viscosity grade scale and the engine will suffer suboptimal performance and protection, if not actual damage.
Some smaller import and domestic engines do not tolerate viscosity changes well. For example tiny valve train components with very small clearances may experience a stacking (hydraulic) effect when heavier oil is used regularly. Over time this can result in valve train damage and even broken valves due to fatigue. Follow the engine manufacturers recommendations with regard to the weight of the oil you run.
Sometimes different viscosity oils and formulas are needed within the same racing discipline. Top Fuel dragsters require 70W while Pro Stock racers run the thinnest oil possible, around 0W-5.
There is a difference between viscosity (a measured value) and viscosity grade (which spans a range of measured viscosity values). The measured viscosity of a particular oil changes constantly with temperature. The viscosity grade of an oil (e.g. 10W-30) does not change unless the oil is actually damaged.
There are three parts to the SAE viscosity grade. The last number (20, 30, 40, etc.) defines the “major” grade. It is determined by the oil’s measured viscosity at 212°F (100°C) and is the most important part of the viscosity grade. It should be considered the operating, or effective viscosity grade of the oil. The “W” stands for “winter”, and not “weight” as is commonly believed; and the first number combined with the W is the “winter grade”. The winter grade of a multi-viscosity oil is determined by two parameters: the Cold Cranking Viscosity; and the Pumping Viscosity. These viscosities are defined as maximum viscosity values at various sub-zero temperatures. All of this is defined by SAE J300 (see chart).
The selection criteria shown in the chart (below, courtesy of Royal Purple) influence the optimal choice of viscosity grade. For example, two identically built engines would likely have different optimal viscosity grades if used in different racing disciplines.
“Operating temperature really impacts oil formulation and viscosity selection,” warns Speed. “High-temperature applications like Sprint Cup utilize different chemistries than low-temperature applications like Pro Stock.”
Matching viscosity to engine clearances
Viscosity must be properly matched to the engine’s clearances and operating conditions to optimize performance. If an engine is not built to take advantage of light viscosity engine oils, the oil may not be able to adequately “fill” the oil clearances and fail to adequately support engine loads. On the other hand, heavy viscosity grade engine oil does not automatically equal better protection.
“Oil film strength and high-temperature, high-shear viscosity are the essentials to providing optimum bearing protection,” says Negast.
Selecting an oil viscosity to match bearing clearances is especially important in a race engine.
There’s an old engine builder’s adage about clearances says that “loose is safe.” That’s generally true, but some builders flirt with disaster by running wider clearances and using thinner oil that can’t support them. The pressure distribution of any bearing is typically greatest at the center and tapers off toward the edges as the bearing discharges oil to the side clearance. Hence, wider bearing clearances require a higher viscosity oil to maintain the hydrodynamic oil wedge while tighter clearances will support thinner oil at the right pressure.
“Whether you realize it or not, you build your engine around the oil so matching viscosity and clearances is critical,” says Speed.
Some street performance oils balance higher ZDDP levels with less detergent, but you can still race and change every 3,000 miles. Others do not sacrifice detergency and oil cleanliness, and still maintain exceptional wear protection for extended drain intervals. The oil manufacturer’s tech line should be called to determine the useful life of their products.
Racers, however, must be aware of oil condition at all times. Oil is easily diluted when using nitrous or alcohol.
“Some racers will try to burn off the alcohol and reuse the oil,” says Negast.
Many oil suppliers offer special formulas designed to help break in an engine properly. Builders can then switch over to the desired oil for race or street use.
Specially designated break-in oil is a must for all fresh engine builds/rebuilds to ensure adequate wear protection for the valve train, while allowing the new piston rings to seat to the engines cylinder walls. It provides a balanced package, plus corrosion resistance and rust and inhibitors. Engine builders can then switch to the preferred racing or street-performance oil.
“Once a new engine’s parts have achieved compatibility with a good high quality break-in oil,” confirms Speed, “most street engines can still operate safely on modern over-the-counter street oils.”
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Up to 500-600 Hp likely Be OK with a 10w30 premium oil.
If Your shooting for 900-1000+ HP Power adder have to reconsider.
Opinions will differ.
Everyone is right till that drag race engine blows up.
All Buds will be gone.
Its just you and the oil choice you made.
20w50 Race Oil For Hot summer time race use when its 80-100 F outside my pick.
Street I use 10w30.
I went through all Factory GM Service Manuals for Pontiac V8 1959 - 1970.
1965 Olds 425.
Interesting oil specs.
Not far off from today.
10w30 was around in 1959.
Hot weather 10w30 was Ok.
But 20W was recommended instead.
20W40 came about in 1970.
Pontiac specific stated to use straight 30W or 10W40 at all times in Ram Air Engines.
Be RAIII and RAIV.
Not on the internet anywhere till now.
I never liked Loose main & rod bearing clearances in a Pontiac V8.
They were all Tight Clearance motors Day one.
Same with Oldsmobile V8 2nd design come 1964 330 & 1965 425 ci V8.
In the Factory service manuals I have.
I have used 20w50 in Pontiac V8 & raced with it, worked.
There is a fairly new oil viscosity not well know but used by High End Euro car guys.
Specified by Ferrari, Bughatti for the Vernon H-16 1100 HP engine, BMW, Austin Martin, AMG Mercedes.
10w60 spec oil.
Stuff is expensive only comes in full synthethic.
Only Big Name brands That make I recognize is Castrol Oil & Royal Purple.
Royal Purple XPR is the only to specify OK for Nitrous use 5w30 & up viscosity.
The Oil temps in Vintage Musclecar engines were sky High in high temp weather & GM Engineers knew it.
Why 20W or straight 30 W called for Racing or High Temps. No such thing as 20w50 in 1970 it was not invented yet.
Read 1st hand testimony on the Olds forum.
260-300 F oil temps does happen often & most never know it. No oil temp gauge probe immersed in oil in the oil pan sump.
I just placed my order for 2 cases of Kendell 20w50 GT-1 Racing oil Dino Grade.
Pretty good deal at around $5 per quart.
High Zinc & Phoshourus needed for Racing use.
Bought 6 quarts of Royal Purple XPR 20W50 Racing Oil.
Used Summit Racing.
Supposed to be best for high rpm High Hp Race use in Hot Summer weather.
Stuff is expensive at $17.50 per quart.
Don't use Amazon for Royal Purple.
Gave it 3 tries last few weeks.
Had to return each time.
Sent R.P. HPS. instead.
Not XPR 20W50.
Got my refund from them.
Corvette and Chevy Tahoe I use Castrol GTX 10W30 .
That's a good deal Brian. I was paying $8 qt. for VR1 20W/50 last year. I see it is on sale for $6 qt now
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