Ive used Seafoam on used cars before and I know they do make a difference on older cars. But for new ones, do they actually have any real benefit? Maybe something like preventing gunk from building up?
I've found that a clean engine comes from:
1. I use only top grade 100% synthetic oil & change oil & filter every 8,000 to 10,000 miles.
2. every 5,000 miles I put one bottle of Chevron fuel injection cleaner in an almost empty gas tank, fill the tank with 89 or higher octane gas and drive until the tank is almost empty again. (Do NOT refill tank until almost empty or it will dilute the cleaner.)
This cleaner seems to be the best in my experience. It really does make a difference. Toyota dealers also have a good cleaner that runs the same way.