well i noticed a mileage upgrade when i put the Custom CAI on my car, then i always put fuel injector cleaner in once a month, even though i use premium, keep my tires properly inflated, and use the cruise when i get on the highway usually at like 73-75 cause the speed limits here are like 65
but who really follows those silly things anyways?!!!LOL!!
Plus regular routine maintenance helps as well and my car came with a magnaflow exhaust system and a new O2 sensor replacement also helped, costed some, but helped. Thats just what i do to my car regularly and what i have done and have noticed it gets really good mileage usually like 20-25 in town driving and 30-34 on highway. i made it once from corinth, MS to Ohio on one tank of gas and the others that i was following had to stop 2 times!!!