Crankcase flush products, any harm?

Brett Dikeman quattro at
Fri Mar 25 01:59:22 EST 2005

TWFAUST at wrote:
> I keep hearing that crankcase flush products (I think Gunk makes one) will do 
> terrible thing to your engines internals. I have heard of anyone who actually 
> suffered from the use. I have used them a few times, I think the Gunk 
> product, and never had any trouble. Is this just an old wives tale? Can anyone 
> actually verify dire consequences?

Nope.  Stick to the instructions on the can, don't even think about 
driving with the stuff in the engine, don't use it if it will fill the 
oil level past maximum, don't run the engine longer than they say to, 
and don't rev the engine too much.  Most are supposed to be used on a 
warm engine, as well.  Oh, and watch out when you pull the plug, since 
the oil will be hot AND more viscous.

It's not necessary unless the engine has varnish buildup and whatnot.  I 
think most people just run a good synthetic and let the detergents in 
synthetic do the work over the course of an oil change or two.

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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