Two questions regarding improving gas mileage: performance air filter and water plus gas?


What do you think of the claim that certain air filters like the KN high performance filters improve gas mileage and power? Is it true?


What do you think of the claim that cars mileage improves with a combination of water and gas? For example go to:



No and a load of male bovine droppings, respectively.


The K&N type filters MAY increase gas mileage…but at a cost. It does it by not filtering as well as the OEM style. And since for every gallon of gas your car consumes it will consume 10,000 gallons of air…personally I’d like that as filtered as possible.

As for the Water for Gas…It’s a total scam. Why the FTC can’t arrest these people I don’t understand.


The K&N air filters may provide a marginal increase in power but any such increase will cost you mpg. You can’t have it both ways.

The numerous water4gas schemes are all swindles. There is no doubt.


The K&N filters won’t improve your mileage and may cause problems with your Mass Airflow sensor. Stick with the OEM system.

The water thing is a scam.


Since this remains the OP’s one and only post here, I wonder if the “water for gas” scammers have come up with a new angle to try to disguise their spam posts: add a second question.


The K&N filter could increase your mileage, but it is not likely you will be able to measure it. It will be small at best. It also may damage your MAF (Assuming your car has one, you did not tell us what you drive). If they are not oiled just right, they can damage an MAF.

The water thing is just a SCAM. It has been around for years and has never worked. Hint, it can’t work because it would be violating a law of thermo dynamics. You might be able to violate a speed limit issued by the government, but you can’t violate a law of physics.


Could be, but that would be assuming that they had any sense. Since they are debunked as fast as they post the message, it would seem to be a no winner for them either way.


The intake air of most cars, especially those being driven for maximum fuel economy, is already severely restricted by a nearly closed throttle. Do you really think that an engine cruising with the throttle only 10~20% open even notices the extremely minor extra restriction of a stock air filter?


There must be warehouses full of “water injectors”, a 70’s scam brought on by the Arab Oil Embargo, that promised better gas mileage. I suspect the cobwebs and dust are being cleaned off in preparation for a gullible public. Of course they will change the packaging and add a “Green” label, ensuring countless sales.


The air filter, like a K&N or AIr Grabber by Fram will help. The more air available for combustion the less waste. Water is never a good fuel additive.


More air without more fuel equals a leaner fuel/air mixture which often makes fuel efficiency worse. More air with more fuel means more power which means you have to close the throttle more to keep from speeding. A closed throttle is a huge airflow restriction, in fact that is the whole purpose of a throttle.
With modern closed loop fuel injection, the oxygen sensor in the exhaust is what controls the fuel mixture and it doesn’t care whether it is the air filter or throttle that is restricting the air flow.

The air restiction through a closed throttle is very parasitic and reduces the efficiency of an engine dramatically. How do you get around this problem? Shift gears as soon as possible is one way. Using an engine that is well matched to the task is another, there is no more in-efficient way to make 20 horsepower than using a 100 hp engine throttled down to 20 horsepower, except maybe using a 200 horsepower engine throttled down to 20 horsepower.
A lot of gas mileage records were set by accelerating at full throttle and then freewheeling with the engine switched off and repeating over and over. This is called “pulse and glide”.