JHZR2
Staff member
Hi,
Had my 98 Chevy S10 in for service and was talking to a very knowledgable technician. One thing I asked was about oil viscosities, and if he thought something like a 5w-40 would be better for the L35 4.3L V6 in my truck. I told him that I wondered about using heavier oils because my sources have stated more or less that tolerances and clearances havent really changed at all in a long time.
He said that the reason for this was that engines now use 'low tension piston rings', which have less friction and less pressure against cylinder walls. Since there is less pressure, a thinner oil can be used and still provide an adequate (or sometimes better) film. Also inferred that bearing tolerances should always have an adequate flow of oil to provide a good protective layer, so long as oil pressure is sufficient, and the fuel isnt too thin, i.e. diluted with coolant or fuel, etc. He said that the 5w- oils are mainly for fuel economy in cold engines, and for these engines a 10w-30 oil (particularly synthetic) would be the best protection, although 5w-30 is preferred for all climates. 5w-40 would do nothing but rob HP.
So a lot of what he said is exactly what we have been saying here for a long time. However, I notice that most of the discussion is about bearing tolerances and oil weights, when he seemed to suggest that piston rings, and their respective pressures on the cylinders, etc. were an important factor.
Any comments? I know it seems that the LS1 engines have been successful with 40wt oils, and I know my 4.3 is essentially a 350 with two cylinders cut off. But Id bet the designs of a lot of things are different, particularly because one is a car engine, the other for a truck. I had a good analysis one time using rotella synth 5w-40, as I got 8.5 ppm after 3000 miles on this all iron engine. But I did feel like power was a bit less. Im thinking of going to M1 10w-30 next, as I know this is a highly regarded oil, but we shall see. That 0w-30 racing looks good and is probably a bit thicker than the m1 30weights that tensd to be quite thin.
JMH
Had my 98 Chevy S10 in for service and was talking to a very knowledgable technician. One thing I asked was about oil viscosities, and if he thought something like a 5w-40 would be better for the L35 4.3L V6 in my truck. I told him that I wondered about using heavier oils because my sources have stated more or less that tolerances and clearances havent really changed at all in a long time.
He said that the reason for this was that engines now use 'low tension piston rings', which have less friction and less pressure against cylinder walls. Since there is less pressure, a thinner oil can be used and still provide an adequate (or sometimes better) film. Also inferred that bearing tolerances should always have an adequate flow of oil to provide a good protective layer, so long as oil pressure is sufficient, and the fuel isnt too thin, i.e. diluted with coolant or fuel, etc. He said that the 5w- oils are mainly for fuel economy in cold engines, and for these engines a 10w-30 oil (particularly synthetic) would be the best protection, although 5w-30 is preferred for all climates. 5w-40 would do nothing but rob HP.
So a lot of what he said is exactly what we have been saying here for a long time. However, I notice that most of the discussion is about bearing tolerances and oil weights, when he seemed to suggest that piston rings, and their respective pressures on the cylinders, etc. were an important factor.
Any comments? I know it seems that the LS1 engines have been successful with 40wt oils, and I know my 4.3 is essentially a 350 with two cylinders cut off. But Id bet the designs of a lot of things are different, particularly because one is a car engine, the other for a truck. I had a good analysis one time using rotella synth 5w-40, as I got 8.5 ppm after 3000 miles on this all iron engine. But I did feel like power was a bit less. Im thinking of going to M1 10w-30 next, as I know this is a highly regarded oil, but we shall see. That 0w-30 racing looks good and is probably a bit thicker than the m1 30weights that tensd to be quite thin.
JMH