In a case where a good quality fuel is always used (we'll use Chevron in this example), is a fuel system cleaner/additive needed? I ask because I've used only Chevron for the almost three years straight in my car. I've used the Techron fuel system cleaner about 3 times to clean up since I don't know what type of gas the previous owner used. Am I wasting $5 for the additive that I usually use twice a year? Thanks guys!