Postby project.r.racing » Fri Mar 16, 2012 9:48 am
NC MZR engines like 5W40s 0W30s.
NA6/8 B6 and BP engines liked 10W30 (back when the handbook was 1st printed).
As said I posted earlier, advancement in oils etc, means 5W40 synthetics are close to what old skool 10W30 minerals were in the early 90s.
All oils have a data/product sheets, this give you the cSt (centistroke)(viscosity = ability to flow) at pouring temp, 40C and 100C (operating temp). This is the info you need to make a decission about your oils. And then there are so many varibles that go into it, that it is like trying to measure a ball of string trying to answer which oil is best.
As I own both a BP and MZR engines in 2 different cars, I did some research a while back from only Penrite products:-
Penrite HPR 0 00w30 64.0 cSt @ 40C, 11.4 cSt @ 100C
Penrite HPR 5 05w40 92.0 cSt @ 40C, 15.0 cSt @ 100C
Penrite HPR 10 10w50 127.0 cSt @ 40C, 19.0 cSt @ 100C
Penrite HPR 15 15w60 177.0 cSt @ 40C, 24.3 cSt @ 100C
Old skool mineral 10W30s have average ranges of 65-75 cSt @ 40C and 10.5-11.5 cSt @ 100C. So as you can see, a 0W30 fits close to the bill compared to older 10W30s. Then you've gotta throw into the equation age factors, it is buring some oil at high rpm? It is got worn valve stem seals? Does it get used on the track (so @ 150C operating temp)? What are the service interval time lengths? Etc?
Also one thing to note, and this comes back to the handbook printed in 1989. It was printed with info current for 1989. Oil technologies etc have advanced so much, that reading the handbook about what fluids to put in the car will just send you in the wrong direction.
Reading that handbook is like reading a navigational book that says the Earth is flat. It is just a little outdated for our current time.