He he. the ouside temp all year round i 50F
I have talked with castrol and valvoline
Castrol recomended Castrol GTX 10W-40 A3B4 asked for how much ppm zddp it was in the oil. could not answer.
valvoline :
"Extra ZDDP we have in our VR1 Racing oils.
These are available in 20W-50 (mineral), in 10W-60 (semi-synthetic) and 5W-50 (full-synthetic).
In our recommendations on the Chevrolet 1984/85, viscosity is 10W-40 or 20W-50.
With this as a background, I would recommend the VR1 Racing 20W-50.
If you get closer to the specified viscosities, the 5W-50 will be an option - but it's synthetic. I would check that it was OK at first."
I have bought 1 bottle of addition from Comp Cams and 2 bottles from STP with Zddp.
Its too cold where you live for 20w50.
You Need 10w30 Oil for 50 F & Colder.
10W40 works flows best 75-90 F temps outside.
Thick Oil just does not flow on cold engine startups in Cool or cold weather.
Severe wear will take place on the Engine Main & Rod Bearings.
I use Castrol 10w30 Edge Full Synthetic in my cars and trucks here in the USA.
My 1963 Pontiac Grand Prix with its 1965 Oldsmobile 425 Engine I transplanted in I use Conventional Castrol 10w30 .
I used to use GM EOS all the time.
I quit using it about 1-1/2 years back.
Was using Castrol 10w30 Edge in it.
It runs fine on Conventional Castrol 10w30 .
No Flat tappet cam issues.
Comp cams has a terrible rap for Cam Lobes going bad flat.
Flat Tappet & Roller cams.
Be sure to add ZDDP.
STP has hardly any Zinc left in it.
US EPA made them take nearly all out.