does adding a cold air intake decrease or raise your gas mileage?
Modern vehicles are factory equipped with a cold air intake, cool dense air is desire able for economy and performance. An aftermarket cold air intake will only be an improvement if your factory design is restrictive or poorly drawing fresh air. An improvement of mileage is unlikely; the original intake is allready pulling cool air and a flow capacity increase is irrelevant when light throttle is being used trying to attain mileage.
It depends on how you drive, a cold air intake raises engine efficacy. If the car is driven conservatively the MPG should improve. But if it is driven aggressively the performance will be better and I don't think any improvement in MPG will be noticed. So yes and no.
