My 2 cents worth. Put 10W-30 back in unless you live where you expect the temps year around to stay consistently above 50 degrees F. To justify this, in the 1990’s car manufacturers went to recommending 5W-30 year around in the northern half of the US. I bought a 2001 van new and the recommendation is 5W-20 year around! Twenty five years ago my dad (a mechanic) told me that he had seen more engines ruined from using too heavy an oil than from using too light an oil. Seems the car manufacturers caught up with his knowledge about 25 years later! The reason my dad gave was that almost all of the wear in an engine happens the first 15 seconds after start-up in a cold engine, or basically while waiting for oil to get to the moving parts. In colder temps, lighter oil can move in between the close tolerances of engine bearings and ring to cylinder wall areas easier and quicker than heavy oil, to lubricat those potential friction areas. To boot, 30# or better oil pressure at idle is nothing to worry about. If you live where the temps are 100+ then go with the heavy stuff. As a kicker, my uncle has an old olds with a 455 in it that has 190,000+ miles on it. The only oil he has ever put in it was 10-10W. Still doesn’t use oil and runs great! Again, just my 2 cents worth!
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