Best oil for V8

paul2748 said:
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.
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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
 
paul2748 said:
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.
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ALL modern motor oil is detergent oil. They ALL have detergents as well as anti-wear additives. The only oils that are non-detergent say so right on the container, and also contain ZERO anti-wear additives. They should NEVER be used in any kind of internal combustion engine.

Detergents are added to hold/suspend contaminants in the oil until it can be drained. This prevents sludge from forming. Modern oils are FAR better than what was available 30-40 years ago. Many of us remember opening up an engine and it being one huge, nasty grease pit! Modern oils don't do that unless oil change intervals are pushed WAY past their recommended time frame.

The main way people break loose sludge in a way that it clogs up passages is by using flushes. Some will add a quart of two of diesel/kerosene to the crankcase and idle the engine for a while before draining. This can help dramatically in clearing out sludge, but it can also clog up drainbacks, etc. Proceed at your own risk. lol
 
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