Does a car air filter improve gas mileage, or not?

Well it depends on the quality of the car air filter itself. If its cheap to buy and built poorly, it usually will not benefit your car from extra fuel economy, power gains and a louder engine. But if you buy a expensive air filter, from a big quality brand called K&N, you will get a slight affect on gas mileage and a little torque and horsepower, although its not noticeable to most people. Most people buy a air filter for better fuel efficiency and economy, why not just get your car converted on lpg? Its more expensive to get it installed and fitted, but it is more effective on saving your car's fuel and saving you money, if compared to a air filer.