Cold air intake

so in my battle to increase engine efficiency, errrr get better MPG out of my car, i have stumbled across conflicting reviews about how cold-air-intakes can or cannot improve the MPG of a car. it is unanimous that they improve HP, but what is the truth about MPG from this aftermarket device? FYI, I have a 2005 corolla le that is pushing 35mpg combined right now, but i want better!! greedy?? no, frugal! haha thanks for the help

I also have a Corolla, and get 38 mpg in normal highway driving, and 32 in the city. Your mileage is normal, and no add-on devices will improve on that. Improving your driving habits can add cosiderable mpg, however. Drive gently, don’t exceed the speed limit, do not idle unnecesarily, etc. all add to fuel economy.

Good luck!

I know of no reason a CAI will increase mileage, because they do nothing to improve engine efficiency at part throttle. Wide open, sure, that’s where there might be some hp to be had, but at part throttle the CAI doesn’t matter. Also, I’ve seen very cheap CAIs on Ebay, I’d avoid them, hate to think about something breaking/not fitting correctly.

Basically a cold air intake does two things. One, it is a lower constriction air filter/air box design that allows more air flow. But this has the EXACT SAME effect as opening the throttle more. So, to borrow a line from Spinal Tap, the net effect of a high-flow airfilter is basically making your throttle go to 11, which might squeeze out a few more horsepower at full-throttle acceleration, but if you’re driving for economy the benefit is zero.

The other supposed benefit is that the cooler air coming in from a lower position will be less prone to premature combustion than heated air coming from a position closer to the engine, having a similar effect to running higher octane fuel. Of course, if your engine is otherwise stock, it’ll runs FINE both on regular octane fuel and on warm air and there is no benefit to either premium or a CAI.

The cold air intake should increase power by virtue of increased air density at the throttle. The engine can burn more gasoline at a given rpm if the intake air is cooler and more dense. This effect will be pretty small though. Who knows how much difference in air temp there will be between the stock setup and the CAI? Most of the cars I’ve seen take the intake air at the front of the vehicle anyway and this should be pretty cool air. Some CAIs I’ve seen move it off to the side and lower it a little. 10 degree temperature difference would only increase power by about 2%. I agree with the others that MPG would not be affected.

One thing to watch out for: if you lower the air intake, the engine is more prone to hydrolock if you drive through deep water, or even a deep pothole or a “just wrong” heavy splash. Say good-bye to the engine if it snorts up a big slug of water.