Correct oil viscosity?

[123finboy]

I have '58 with the 332CID, 4bbl V8. The shop manual says to use 20W oil when the outside temp is above 32 degrees F. Since I live in the deep South, that temp describes most days, so no problem. I've also been told, that because of our long hot summers, I should use 20W50 to better withstand our 100 plus degree days, as well as defend against any minor gas leakage from the carb should that occurr. Does this make sense? Will the 20W50 have any effect on oil pressure?

And one more question, is a 20W50 oil basically a 20W oil with viscosity enhancers for higher temps, or is it a 50W oil with viscosity reducers for lower temps? Thanks in advance.

Finboy

 

[Ole Don]

For your viscosity question, check with Bobstheoilguy online. One thing to consider with any old engine, with the modern additive package to extend the life of catalytic converters, our old engines need oil meant for different engines because we still use non roller lifters. To ease problems, I use Shell Rotella in old engines. It too has changed, but look for any oil with 1000PPM zinc. Rotella is available in 10W30, or 15W40. The later easy to find anywhere. Both still have the required 1000 PPM zinc for our cams and lifters.