A little known fact for keeping valves clean of carbon deposits is to add about 1 cup ATF oil to your oil changes to remove varnish off of the valves.

Keeps the price down for using Engine additives in your Gas tank.

 

is that safe for the motor?

 

I think the tip needs more information. If you were to use ATF to clean deposits, do it a couple hundred miles before your next oil change. A quart at most. Moderation. Misc seals in your engine will not like being overexposed to ATF. I have not seen research anywhere that states ATF is safe to run in your engine on a consistent basis. I have, however, heard some horror stories from using too much concentration of ATF(gasket leaks). That's my $.02

 

I've only heard of running ATF through your engine for like 15-20 minutes to clean out the crankcase area of any gunk inside. I do this EVERY year, not everytime I do an oil change, Reason being ATF is a detergent oil and will deteriorate any seals that are weak or going bad. 1 time a year is good enough to keep sludge from building up. and if you do your oil changes regularly you won't have a sludge problem anyhow.

As far as carbon deposits go I suggest seafoam cleaner into the intake chamber via a vac. line, let the engine IDLE and add in the seafoam just enough to keep it running for about 5 minutes this cleanes the engine of carbon REALLY well and it runs GREAT after your done. All the dealerships use some form of seafoam to do an injector service.

Troy