Best oil for V8

[cadillac512]

Originally Posted by paul2748

What's the truth to the old saying that you should not use a detergent oil on an engine that you don't know the condition of i.e. sludge, deposits, etc.



Some people say it can loosen up the deposits and clog passages.

Although I've tried it several times, I've yet to see any sludge loosened by modern oils. That stuff is so dense and settled/attached that only scraping and serious disassembly and cleaning will remove it. I ran a high mileage flathead 3000 miles burning a qt of 15w40 high detergent diesel oil every 200 miles (during summer) and the sludge wasn't affected at all. About 1/2"+ deep in the pan and large amounts in the valve chamber. Stuck like glue.


Terry