[Jay S]

We have multiple old street and strip engines in cars that are 30 some years old with 10w30, 15w40, and a couple that have 20w50 in them. I have never seen the need to drop lower than 10w30. I just run 60 psi pumps though.

We ran 20w50 in the 455s in dirt track race cars. My avatar photo was a 466 CID 3.25” main Pontiac. That one would get up around 6500 at the end of the straight away on nights the track was sticky. The main feature was a 25 lap race on a 3/4 mile track, sometimes would go 40 laps a night if it had to go up thru the features. That is definitely a different kind of abuse than drag racing! Only could go a few weekends on an oil change. The first engine we did the oil clearance was pretty tight. We kept opening the oil clearance up to make the bearing last better. The last engines we did, had .0025” to 003” on the rods and .003 to 0035” on mains, and by the time the remote oil filter and oil accumulator were filled, it held about 14 quarts of 20w50. By the end of the night, the radiator would start to get plugged up with mud, and your watching it go down the track past 6000, never dropping below 4000 anywhere while it is over heating wondering how on earth it is still running.

On the flip side, I know a lot of the worry about oil weight is unfounded, and I personally would say that goes both ways with in reason… thick or thin. A good 5W20 is pretty darn tough too.. I ran into one engine with Valvoline semi synthetic 5w20 that was started on a cold day (-28*F) and the oil filter partially collapsed. After that would randomly loose oil pressure while driving. Replaced the sensors and it still did it. Shut it down and start it up and the pressure would come right back. I thought it may be an electrical issue. It was driven months like that, once it went 10 miles with no oil pressure registered at all and didn’t make a sound that indicated it had trouble. Finally it got worse, it had a oil temp gauge, so I also watched the oil temp to see if it rose. I drove 6 miles at 70 mph at 2500 RPM and nothing changed, oil pressure at zero. I thought for sure it was electrical, but mile 7 it gained 1 degree, mile 8 it gained 5* and I shut it down. I let it cool down, started it back up and it was fine again. But it started acting up right away, end up hauling it home. I changed the oil filter and we put a few thousand more miles on it. I end up overhauling it, the cam was what went bad. I got into it and found out it was a Reman engine, and someone had forgotten to put the back cam bearing in. LOL My point in mentioning that is it really isn’t that often that oil that is changed in the correct intervals is the blame for engine bearing failures.