Originally Posted by Jimbo
quote:
Originally posted by Ugly3:
Just keep in mind the number of "loose" engines that ran on 20W oils in the old days. Those 20W oils were not up to par with the 20W oils of today. Why are we concerned about a new engine being speced for a 20W oil?
How long did a typical car last in the 1950's before being junked, or at least needed internal engine work, 60k miles? OCI's were in the 1-2k miles range as well. We expect about three times the service life on one third the rate of oil changes today. It was the elevated temperatures of emissions controls that led to thicker oil specs in the 1970's, but it seems that average engine life also took an upturn at the same time. Granted, with modern oil chemistry, we can go thinner again without going back to 60k mile engine life.
On the topic of pour points, SA-rated straight 30 (Coastal) was hard, like rubber, at 0F in my freezer test. You could actually see the wax crystals in it.
I think they had a lot more things going for them in the 70s for longevity. Axle ratios, unleaded fuel, better oil, lower RPM (smaller camshafts for emissions). My 1976 350 Oldsmobile in my 84 Cutlass would have likely had a 2.56 axle ratio, a catalytic converter so unleaded gas, and it doesn't go over 4500 RPM. A 1966 engine would likely have had a 3.50 or lower gear ratio, leaded gas, larger camshaft, more horsepower and higher RPM. It may have seemed like the dark era for cars at the time but the 70s were good for longevity except for the first economy cars like the Vega, Pinto etc that were kind of a big failure.
I don't know how many miles are on my 76 Olds but I've put over 100k on it the past 13 years with modern synthetic oils and I suspect it had high miles when I got it from the junkyard. It didn't appear to have ever been apart.
