I have a 1999 Accord V6 Coupe (J30A1) with 150K on the car. Do you think it would be a good idea to seam foam it?

 

Used properly, it will do no harm.
Personally, I use GM Top Cylinder Cleaner
They are both de-carboning agents

P

 

I'm interested in this as well. At what mileage (average driving habits and regular maintenance done) would a "deep internal cleaning" like this be recommended...or is it even necessary?

 

I wouldn't say there's a specific mileage persay, there's no reason to do it on a new motor because there's no gunk. However at ~150k I can tell you my EGR ports were horribly gunked up and I wager seafoam would definitely benefit it at that mileage.

Perhaps P or someone else could chime in.

 

LUCAS FTW They Make Some Good Products. Instead Of The Sea Foam Use Lucas

 

This is a group of products (specialty chemicals) which were developed to address certain conditions which could arise during operation. I have yet to see a Maintaince Schedule or a product recommendation based on an interval for these.

Seafoam and GM Top Engine Cleaner are De-Carboning agents. They were developed to remove carbon from:
Combustion Chambers
Piston Tops
Valve Stems
I've been using them to free up stuck Piston Rings.

Rislone is a product developed to Clean Crankcases and oil passages of sludge buildup by desolving it.

Etc.

P