I understand oil has come a long way but I think the most important aspect of our older v8-s with miles on them has been overlooked.
Viscosity is the most single important thing to our old V8-s. Just like a modern small clearance motor lives well on 0-20 it would not last long on 15-40 because it was not designed to.
Even current oil for high mileage motors 75k and above of the three main things they offer, one is a viscosity modifier to prevent premature viscosity breakdown.
To maintain the oil film between the bearing and shaft so the bearing isn’t starved for lubrication. This also requires more oil pressure from the oil pump and/or more oil volume. Running a thinner oil does not achieve this. The piston ring design, gaps, and the pil control ring was not designed to deal with a thin oil.
The 80-s 318 spec the same clearances as a 1972 318.
Even modern engines with high miles are subject to needing a bit more viscosity.
What makes high-mileage engine oils different?
High-mileage oils have ingredients to take care of older engines, like conditioners, seal swells, antioxidants, detergents and wear or friction additives. Typically they use a viscosity modifier that is durable and won’t lose viscosity very easily. These oils need to stay thicker longer to protect engine parts.
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I myself will never use a modern synthetic in an dino designed motor, 15-40 rotella T4 minimum.
We may not like the stresses thick oil put on parts but we cant dispute the reasons why it is needed by the engine design itself. And most folks are running aged semi high mile motors.
Yep, if it was above 0 we could still and would run straight 30 weight and so it cranked slow, it was expected. For 100 degree summer heat 40 or if it was real loose straight casrtrol gtx 50 weight. Thick and green.
The only reason a mostly stock 318 fmj car really can go against the grain is the gearing produces a very low rpm at even highway speeds. Take a 318 with 125 more hp, 3:91s to 4:56 gears and run down the highway at 3k or bettr rpm with a 10w anything and budget for a crank kit.
Im not saying Asp500 is wrong but I will say our older motors most important oil requirement is based on viscosity and although modern oils have came a long way the viscosity rating system has remained contestant since 1952 although the SAE ratings started in approx 1911 but was modified in 52.
So if you are going to run a 10w oil id consider the high mileage version.
Oil is always a controversial topic
