For injection/fuel cleaning I would just do it every 25k miles, Anything more then that is a bit overkill.

 

There is no reason in the world to have carbon build-up at 20K miles on a rev-happy 4-banger. With modern fuels, this simply will not happen. Unless you're like my dad and you never rev past 3K rpm, you won't have a single molecule of carbon build-up. And with modern synthetic motor oils, varnish and sludge are basically non-issues (especially if you change the oil at <5K mile intervals).

Your dealer is full of it.

To the guys recommending Seafoam and other products, please remember that these are petroleum solvents. They really do a number on seals, gaskets, and other rubber/plastic parts in your engine and fuel system. This is not a 50-year-old Chevy truck we're talking about here! There is no need for this stuff on a modern engine that's driven hard and maintained well.

If you're really worried about sludge/varnish, just change your oil regularly and use high-detergent oils (like Mobil 1 or Castrol Syntec semi-synthetics). If you're worried about carbon build-up, just use high-quality gas from name-brand vendors (Chevron is the best). And rev the **** out of your engine from time to time. An engine that gets revved regularly will NOT develop any significant carbon build-up. If you're still worried, just add a bottle of Chevron Techron with each oil change (every 3K-5K miles). That will keep your injectors, fuel system, and intake valves nice and clean.

Emre

 

Would be great if I had a Chevron or Texaco... but the best gas station around me is Sunoco... which is the only one for about 200 miles. Sucks when I'm short on gas 25 miles from my house.

 

I didn't say it was dealer's fault. The guy realized later that it wasn't worth it