1. How will a K&N filter affect my vehicle's fuel economy?
2. What increase in horsepower should I expect from a K&N replacement filter?
3. What increase in horsepower should I expect from a K&N air intake system?
4. How often do I need to clean my K&N air filter?
5. Can a K&N product cause my Check Engine Light or Service Light to come on?
6. How can I tell the size of the engine in my vehicle?
7. Can a K&N filter give my engine too much air flow?
8. Will using a K&N direct replacement filter void my factory warranty?
9. Will installing a K&N performance intake system void my factory warranty?
10. Do K&N air filters come pre-oiled or must they be oiled before using?
11. Should I install the largest K&N filter that will fit in my race vehicle?
12. My filter came with a tube of sealing grease. How important is it?
13. Are K&N filters emissions legal?
14. Are K&N performance air intake systems emissions legal in the US?
15. Are K&N RK-Series Custom Air Cleaner Assemblies emissions legal?
16. How do I clean a K&N air filter?
17. More airflow means you are letting more dirt through, right?
18. Can I use anything other than K&N cleaner and oil?
19. Can I use compressed air to dry the filter faster?
20. Should I brush the wire screen with a toothbrush to get all the "crud" off?
21. Will a K&N filter cause my vehicle's mass air sensor to fail?

1. How will a K&N filter affect my vehicle's fuel economy?

There is a relationship between air filter restriction and mileage. The theory behind this is simple, the harder an engine has to work to suck air through the intake tubes and air filter, the more gas gets wasted in the process. Many K&N users report an increase in their fuel economy after beginning to use our air filters. However, these experiences do not mean you will also experience a change in your mileage. We certainly understand why it is theoretically possible for a consumer to experience a mileage increase after installing a K&N air filter or intake system, however, we do not go so far as to make a general claim that our air filters and intake systems will provide an increase in mileage.

It is virtually impossible to make sweeping and general claims about mileage. Even the EPA fuel rating numbers for new cars are often not representative of the mileage you actually experience. There are many variables that affect mileage such as: tire inflation, the type of fuel, weather, elevation, the speed at which you drive, the gear in which you drive, the speed with which you accelerate, engine maintenance, excessive idling, cruise control, the grade of motor oil you use, and of course, the condition of your air filter. In short, mileage is complicated.

K&N filters are less restrictive than disposable paper or synthetic air filters and K&N Intake Systems are less restrictive than the factory installed air path. So K&N filter technology could be an important tool, when combined with other elements, to help keep mileage as high as possible.

Oh yeah, there's one more limitation imposed by science. If you take advantage of added power by driving more aggressively, you will reduce mileage. You cannot have your cake and eat it too.

2. What increase in horsepower should I expect from a K&N replacement filter?

K&N direct replacement filters which install into your vehicle's factory air box can provide an increase of between 1 and 4 horsepower. Results will vary depending on your vehicle, driving habits, load on the engine (towing for example), existing air system restriction, and other factors.

3. What increase in horsepower should I expect from a K&N air intake system?

K&N makes several different types and configurations of performance air intake systems. Depending on the year, make, and model of your vehicle, only one style of intake system may be available for that vehicle. All of our intake systems are dyno-tested and guaranteed to increase your vehicle's horsepower. Instead of making a general claim, we publish actual intake system horsepower increases for many part numbers and vehicles. To see the power gains of specific air intakes for specific vehicles, enter the part number in our part search or look up a specific vehicle in our application search.

4. How often do I need to clean my K&N air filter?

If you have not experienced a decrease in mileage or engine performance, chances are your filter is fine and does not yet need cleaning. To be more specific, the filter does not require cleaning if you can still see the wire screen on the entire air filter regardless of how dirty it may appear. When the screen is no longer visible some place on the filter, it is time to clean it. When used in normal paved road, street or highway conditions, our replacement air filters that fit in the factory air box should require cleaning every 50,000 miles and our large conical filters on an intake system should require cleaning every 100,000 miles. When used in dusty or off-road environments, our filters will require cleaning more often. We recommend that you visually inspect your filter once every 25,000 miles to determine if the screen is still visible.

5. Can a K&N product cause my Check Engine Light or Service Light to come on?

A properly installed K&N product should not cause the Service Light to illuminate.

6. How can I tell the size of the engine in my vehicle?

North America: Most vehicles have an emissions decal placed either on the backside of the hood, on the radiator core support, or on the air box (the box that holds the air filter in place). Your engine size should be shown on the decal (4.0L for example). If you can't find the emissions decal you may also find the engine size printed on the decal under the hood that shows your engine's belt routing. You may also write down your Vehicle Identification Number that is stamped visibly near your driver's side dashboard top and listed on your vehicle registration certificate. This number can then be entered on K&N's part search by VIN webpage to find engine size as well as products for your vehicle. You may also contact your local dealership.

Europe: Your registration documents detail your engine size and type of vehicle. However, if you do not know whether your vehicle is spi (single point injection) or mpi (multi point injection) we suggest you consult your local dealer.

7. Can a K&N filter give my engine too much air flow?

No. An engine can only draw in a certain volume of air depending on the engine's size (measured by such things as bore, stroke and number of cylinders). Vehicles are designed to accommodate large changes in air pressure so they can operate at sea level or at an altitude of 14,000 feet. Engine computers adjust the amount of fuel required as a result of changes in air pressure (density). Air filter restriction when the filter is new and especially as the filter loads with dust will result in lower air pressure and availability similar to being at a high elevation. High-flow air filters that were invented by K&N were designed to reduce the work necessary to pull air through the filter and to increase air pressure. Increased air pressure is one of the key elements in producing more power.

8. Will using a K&N direct replacement filter void my factory warranty?

It is against federal law in the United States for a manufacturer to require the use of a specific brand of air or oil filter unless it provides a replacement air or oil filter, free of charge, under the terms of the vehicle warranty.

9. Will installing a K&N performance intake system void my factory warranty?

Most K&N air intake systems are warranted for 1,000,000 miles which exceeds the warranty offered on the original factory intake system.

The installation of an air intake system should not void your factory warranty. It is never a bad idea to contact your local dealership and ask them before purchasing the new K&N system whether they will object. If they tell you an air intake system will void your vehicle warranty, please contact us and we will speak with the dealership directly to clear up the misunderstanding. Another idea would be to contact a different dealer who may have a different policy since many dealerships actually sell K&N intake systems.

As an additional level of comfort, K&N Filters also offer a Consumer Protection Pledge. It takes customer service to an even higher level by giving you confidence that when you buy K&N you get on-going support from a team of professionals who will talk directly to dealerships to resolve any questions that may come up.

10. Do K&N air filters come pre-oiled or must they be oiled before using?

Almost all K&N air filters come pre-oiled and ready to use. The K&N filter oil is red. A new oiled filter will appear red-pink in color. Some crankcase vent air filters come unoiled, however, they come with a small packet of K&N filter oil so they can be oiled before use. There are also a limited number of filters with specialty uses which are not pre-oiled. These items will be clearly marked as unoiled. Using an unoiled K&N filter will greatly reduce the filter's efficiency and void our product warranty on filters that come pre-oiled from the factory.

11. Should I install the largest K&N filter that will fit in my race vehicle?

If an existing K&N filter is large enough to provide negligible restriction, a larger than required filter will not affect the amount of air an engine can take in, however, it will lengthen the filter's service interval. A longer service interval can be an important factor when racing in dusty, dirty environments.

12. My filter came with a tube of sealing grease. How important is it?

It is rather important. It helps to maintain a seal on an uneven air box surface. If sealing grease is unavailable, white lithium or synthetic grease will work just fine. Petroleum-based products are not recommended.

13. Are K&N filters emissions legal?

All K&N direct replacement filters are emissions legal. They perform the same function as other types of disposable filters and fit right into the factory air box. K&N's custom, universal or conical air filters are not legal for street use in California or other states that have emission control standards. However, if the intake system you are attaching a K&N cone filter to is CARB exempt, the K&N cone filter will not change that status and will be part of the exempt system. Check your local laws if you are unsure what modifications may be allowed on your vehicle.

14. Are K&N performance air intake systems emissions legal in the US?

All intake systems are legal in most states because most states do not have regulations governing them. So this question really has to do with California and other states that have emission control standards. In order for an intake system to be legal in these states, it must receive an Exemption in the form of an EO number from the California Air Resources Board (CARB). To further complicate matters CARB exemption is issued only for specific part numbers used on specific vehicles. That means a part number can be CARB exempt for some vehicle applications and not others. There is no such thing as CARB Pending. A particular part number on a particular vehicle is either exempt or not. The best way for you to determine the status of the part number you are interested in for your vehicle is to look up the intake systems available for your vehicle in our vehicle/part search engine and check for CARB exemption. If you are unsure whether CARB exemption is required for a part to be legal in your state, check with your local or state motor vehicle or emissions agency.

15. Are K&N RK-Series Custom Air Cleaner Assemblies emissions legal?

The rules for motorcycle intake kits are the same as for air intake systems. Please refer to Question 13 above. Some RK-Series assemblies for specific motorcycles have received CARB Exemption, others have not. The best way for you to determine the status of the part number you are interested in for your motorcycle is to look up the parts available for your motorcycle.

16. How do I clean a K&N air filter?

Use a K&N Filter Care Service Kit, available at all major auto parts stores and a low pressure nozzle-free garden hose. A filter cleaned with K&N cleaning products will ensure a lifetime of performance from your air filter. Instructions for cleaning your K&N air filter are available on our website.

17. More airflow means you are letting more dirt through, right?

No. Filtration testing measures the percentage of dust retained before the filter reaches a terminal test pressure, often 10" of restriction above initial restriction. We use airflow as a simplified term to explain a more complicated physical process. The more precise description is restriction: K&N air filters create less restriction which helps an engine run better. An engine will only use the air it needs and our air filters do not result in an engine using more air than necessary. Rather, they result in the engine experiencing less restriction. The terms airflow and restriction are inversely related. Our air filters provide either less restriction at a fixed airflow rate; or more airflow as a fixed level of restriction. In neither case is more air being used than necessary.

18. Can I use anything other than K&N cleaner and oil?

For best results, we recommend that you use K&N air filter oil and K&N air filter cleaner. K&N air filter oil is a special compound which forms a very efficient tacking agent that helps capture dust. Our cleaner is a non-detergent degreaser. Petroleum products such as transmission fluid and motor oil will soften and destroy the rubber sealing edges. Harsh solvents and gasoline will harden the rubber seals causing the filter to distort (shrink). A mild detergent can be used in a pinch, but care should be taken to fully rinse it out. Rinsing detergent out of a filter is similar to getting soap out of a sponge; it's not that easy to do. Always make sure the filter is dry before re-oiling.

19. Can I use compressed air to dry the filter faster?

No, this can blow the filter material right out of the wire mesh and ruin the filter. Pick a nice day to clean the filter and let it dry naturally. A low pressure air flow such as from an industrial drying machine or blow dryer will help the filter dry more quickly.

20. Should I brush the wire screen with a toothbrush to get all the "crud" off?

No, this could tear up the cotton gauze.

21. Will a K&N filter cause my vehicle's mass air sensor to fail?

No, it is both impossible and ridiculous.

It is impossible because we know that the oil treatment on our cotton is very small (usually less than 2 ounces). Once the oil is properly and evenly absorbed through the cotton, no oil will come off, even under extreme engine conditions. It is ridiculous, because no dealership or service provider has ever been able to provide us with evidence to support this "myth," and in fact, our investigations have revealed that even authorized dealerships are simply speculating and do not have the test equipment necessary to know whether the sensor has failed or why. It is even more ridiculous because some car manufacturers use and sell air filters treated with oil on a regular basis. There are also major brands of disposable air filters that are treated with oil. We all use oil for the same reason, it helps in the filtration efficiency of an air filter.