Seafoam, yes/no
 

My neighbor recommended it. Thoughts (gas and diesel)?

Personally have never used it, but I've heard and read many positive things about it; especially when used on cars that have been sitting for a while. Members who have experience with it will likely chime in as well.

I sucked a can of it thru the vacuum line going to the brake booster in a 2001 Intrigue. The smoke was horrible so do it NOT near your house -- pollute elsewhere ... lol. The car ran like a dream for another year or so before the insurance company totaled it because of hail damage.

Diesel = no. There are other things out there that work better (Diesel Purge is an example).

Gas = Yes. I've used it to clean out the fuel distributor on the SL and it does a good job. The key is to make sure you drive the car enough to clean all that stuff out. You don't really want it sitting around in the fuel system for weeks.

Treat it like an injector cleaner. If you want the manifold or head cleared of carbon, pull it and do the job properly. A "bottle fix" isn't going to help you there.

for diesel its useless.

For gas engines a better option to decoke the top is to use chrysler combustion chamber cleaner, its very potent and will make the tracts, valve pockets and CC sparkly clean in one shot.

But please use it as described only.

From my experience
Do it in the rain, smoke less obvious
After post treatment drive, change oil and spark plugs
Does improve mileage and power, but only if the engine needed it.
Doesn't do as much in the tank, gotta spray it into the intake.

We had an old Izusu Stake Bed with over 300k miles on a 327 Chevy motor that failed the smog check miserably. We sucked a can through it, smoked so bad we though the fire department might show up, but then it not only passed smog, all parameters were at the low end. Two years later, it passed again with no treatment necessary.

Sea foam works but its hard on rings. I would use it once a year.

Thanks everyone.