Spark plug has a black deposit


What is the name of the solution that “loosens” the black deposit on a spark plug?


I like to call it a new spark plug.

Seriously I wouldn’t waste my time trying to clean them.



I agree that new spark plugs are the answer. However to avoid this in the future, make sure your car is not running rich, ie too much gas. This occurs in old cars when the choke stays shut. In newer cars it is the can be due to spark plug misfiring or other causes. The stuff to put in the tank used to be called “Karbout”. It can still be bought, but may be modified for newer engines so as not to interfere with the computer sensors.


Sooty black may mean a misfire or rich running problem.

If this black deposit is somewhat hard and caked this may be oil and the cure for that is usually engine work.

As mentioned, replace them rather than clean them. In the old days one could get away with cleaning plugs but with what I assume is a later model vehicle, misfires are much more noticeable and a cleaned plug may not prevent this.


Wouldn’t it be prudent to locate the source/cause of the sooty plug first?

Perhaps a bad plug wire?


Engine ran for awhile while the oil level was low.

I tryed soaking the plug in gas but that did not help remove the black deposit.


Yes, a bad plug wire can cause a plug to soot up.
OP, you’re going about this all wrong. Soaking a spark plug in gas is no way to clean one, even if it were worth the time.

The only proper way to clean a spark plug, and no one does this anymore, is to use a small air operated plug cleaning device that uses grit to clean them.
Lacking that device, as most do, the only other method is a wire wheel and carb cleaner.


Just replace it. You probably need a tune-up anyway.