Last May, I bought a 1980 Buick Park Avenue. It looks good, but the 350 ci. engine was a little worn. The seller told me it had 320,000kms on it. He also told me that the car needed to have 20w50 oil in it in the summer, and 10w30 in the winter. He didn't tell me why, though. My question is: Why would somebody be using 20w50 oil in a car that calls for 10 w30...is it to cover up a problem with the engine? Would it hurt to switch to 10w30 in the summer? The car runs hot after awhile, especially at idle, but hasn't overheated. It also used to have a small oil leak, if that matters. I would like to know because I don't have access to a good quality 20w50 motor oil and I'd like to switch to a thinner weight oil specifically made for higher mileage cars, because I think that's what it needs right now. Thanks in advance for any help you can give me.
They tell you to use thicker weight oil because of a couple possible reasons: - Poor oil pressure with thinner oil - Oil leaks Thicker oil will combat both of these problems. In the winter, you don't want to run anything as thick as 20-50, because it gets very viscous when cold....and may starve the engine when it's still cold.
I don't know a whole lot about engines, but i'm pretty sure that a leak would cause a constant drop in oil pressure and it wouldn't be too healthy for the engine. And if the seller ran the hell out of it for that far, it could cause some serious probs for the engine that might result in needing a different oil. Or, maybe he just thought it ran more efficient that way.o No:
thinner oil like 10-30, in the summer will have thermal breakdown faster than thicker oil like 20-50.
