The ratio is printed on a sticker inside the glovebox. The fuel filter should be changed every other oil change. I pour the Lucas injector cleaner stuff through mine. Not 100% of the time. My truck seems to like it. I had an injector go bad and it sounded at times like the rods were coming out of it! eek No missing that one. I've seen the videos of them leaking into the valve train area but I never thought my trucks mileage was that bad to check it. shruggy Does this thing have an aftermarket air filter on it?