When manufacturers build cars, they design the cool air intake to accept a perfectly balanced mix of air and fuel in the combustion chamber. Any digression from this can cause an irregular fuel flow or different behavior of the engine.
Can it Help?
Owing to the quietness of intake system, it does have the effect of creating more of a warm air build up in the chamber. The result of this is the use of more fuel. Not a great deal, but perhaps as much as 3-5 miles per gallon. Over the lifetime of the car, that does add up to quite a few miles lost.
Fitting a Cold Air Intake
A cold air intake pulls cold air in from the underside of the car, pulls it into the engine and alters the air to gas ratio. This results in a lower amount of fuel need to power the car. Without a cold air intake fitted, the heat generated from the engine decreases the fuel efficiency, so therefore, having a cold air intake will increase it. The process relies on the cold air circulating the combustion chamber and cleaning it.
It does somewhat confuse the car into thinking that it needs to divert more fuel from the injection, but as the car only uses what it needs, any excess fuel is returned and reused later. Alongside the cold air intake, you can also benefit from adding a performance air filter. This will further assist the cold air intake and make fuel consumption more effective. They do not rely on the old paper style filter and they can be cleaned and replaced easily.