Sea Foam for dieseling 1968 Cutlass [SOLVED]

Dieseling: I have a 1968 Olds Cutlass. It has been dieseling a lot lately. Can you recommend a fix? Will Sea Foam in the crankcase work to reduce this problem?

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Jim D.
Jim D.
2 years ago

Dieseling is often caused by excessive carbon buildup in the chamber hemispheres that gets hot (like charcoal) and causes the fuel to ignite. Could also have a hot spot on a spark plug. I would keep the tank fuel low and regularly add a can or two of Sea Foam Motor Treatment or High Mileage – the higher concentration will work to soften and clean the varnish/carbon buildup as you run your Cutlass.

Another idea is to treat the upper engine with Sea Foam Spray through the air intake – consider you’re running a whole can over the intake valves and into the chambers in a matter of 5 or so minutes. You can also remove the spark plugs when hot to spray into the chambers and let soak for a few days at a time.

If the dieseling is related to stuck/dirty compression or control rings, Sea Foam in the oil will help clean the rings. Add 1 oz of Sea Foam per quart of oil 100-300 miles before your next oil change. It might take a few oil intervals, but Sea Foam in the oil will reliquefy deposits and help the rings return to normal performance. If the dieseling is related to this, that will help.

1 year ago

According to the Champion spark plug website, dieseling is caused by too hot of spark plugs. I put cooler plugs in a 1972 427 and it solved the problem.