Seafoam
Record Breaker
Joined: Dec 2010
Posts: 1,191
Likes: 1
From: Nova Scotia, CANADA
It only develpos issue's if you put it in the crankcase to clean out the oil passages. Despite what that directions say DO NOT put it in with your oil. It will eat away any of the build up the oil seals which in turn cause it to leak. There is a thread like this on a jeep forum I'm on and it's probably 50 pages long with more good then bad (90%good vs 10%bad) stories about seafoam. As with any product there is always going to be some negative things about it. BUT this stuff does a decent job if used properly.
Veteran
Joined: Mar 2009
Posts: 358
Likes: 0
From: clinton/old forge, NY
on an older engine it could potentially lower compression as the carbon build up acts like a seal, i've done it on plenty of engines nothing bad happened yet, do it on the the brake booster line
Record Breaker
Joined: Mar 2009
Posts: 2,181
Likes: 3
From: Battle Ground WA
Carbon doesn't seal up anything, it takes up volume therefor increasing the compression ratio.