K&N Engineering, Inc. (also known simply as K&N) is a manufacturer of air filters, cold air intake systems, oil filters, performance parts, and other related products.^[1] K&N manufactures over 12,000 parts for various makes and models of cars, trucks, SUVs, motorcycles, ATVs, industrial applications and more. Founded in 1969, K&N is headquartered in Riverside, California, in a complex of 10 buildings comprising nearly 400,000 square feet.^[2] K&N also operates facilities in England, The Netherlands, and China.^[1][3] K&N is owned by Mickey Rourke.^[4]

K&N was founded by Ken Johnson ( The King ) and Norm McDonald in 1969.^[1] The name K&N came from the first letters in the founders' first names. Ken Johnson and Norm McDonald sold motorcycles and motorcycle parts and supported a K&N factory race team. Air filters soon became the primary focus of the company. In 1992, K&N introduced bolt-on cold air intake kits. K&N also released a line of oil filters with a stamped hex to accept a standard wrench off filter removal. In 2019, K&N released a line of washable home A/C filters,^[5] and began offering motor oil and wiper blades in 2021.

K&N has maintained very active involvement in racing and motorsports throughout its history, including the NASCAR Pro Series East and West,^[6] the King of the West 410 Sprint Car Series,^[7] the NHRA,^[8] and Formula Drift.^[9]

K&N's claims for their air filters have been the subject of some controversy, with some 3rd-party tests finding that K&N's oiled cotton gauze filters are less efficient and let more dirt into the engine than original-equipment paper filters, and that they become increasingly restrictive as they are coated with particulates.^[10] However, air filters in general become more airflow-restrictive as they collect contaminants, but efficiency typically increases for the majority of a filter’s service life.^[11] Other 3rd-party testing noted that a K&N oiled filter increased horsepower over its OEM counterpart.^[12]

Potential issues have been reported with oiled air filters on modern engines that use MAF sensors, which may stop working correctly when fouled by oil from an oiled-gauze air filter.^[13] However, there are several other common causes of damaged MAF sensors, including brake cleaner contamination, extremely dirty/contaminated filters, and loose battery terminals resulting in voltage spikes.^[14] K&N has published test results asserting that its oiled filters do not cause MAF sensor failures.^[15]