Mixing Oil Viscosity Issues

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
My vehicle takes 8 qts. I have 7qts of 0w-20, and 1qt of 5w-20. Both are Mobil1.

Would it be an issue to mix and put in the vehicle?
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I get similar questions frequently, and yeah, if taken to extremes you can harm any engine by using oil that's too thin or thick in viscosity for the application, but most good quality , mineral or synthetic oil being mixed of a similar viscosity will work ok,
example, if your engine manufacturer lists
10w-30 as ideal your very very unlikely to have issues using some 10w30 mixed with lets say a couple quarts of 10w40 or 5w-20 and yeah, most synthetic oil mixes just fine with petroleum oil
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its the constant supply of oil, under pressure and its constant absorbing and transfer of heat from those moving parts, and the oils ability to prevent direct physical contact of those components that's critical.
youll generally want to select an oil with a viscosity that will maintain a 15psi-20psi reading on your oil gauge, when the engines at idle speed and up to operational temperatures of about 200F, on a newer engine with tight bearing clearances that should be about a 10w30 viscosity


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links contain a great deal of related info
http://garage.grumpysperformance.com/index.php?threads/which-oil-what-viscosity.1334/

http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/

http://garage.grumpysperformance.com/index.php?threads/whats-a-windage-tray-do.64/

http://garage.grumpysperformance.com/index.php?threads/installing-an-oil-pump-pick-up-tube.1800/

http://garage.grumpysperformance.co...oil-passages-and-improved-oil-flow-mods.3834/

http://garage.grumpysperformance.com/index.php?threads/basic-info-on-your-v8-lube-system.52/
 
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