Vavoline VR1 20W50 Racing Oil

My 54k-mile '73 Dart has 5w30 oil in it in Seattle. If I (and it) were in Florida...

...it would still have 5w30 oil in it.

If it had 200k more hard miles on it and I were trying to squeeze every last mile out of it pending a rebuild or engine replacement, then it might have 20w50 in it. A lot of guys get this backwards: they use oil much heavier than appropriate because they "feel" (with zero scientific basis) that it protects better, but in so doing, they accelerate the wear they think they're preventing.