Some dealers still use (and advocate using) the aftermarket 6022 or equivalent. We have rebuilt two engines that were otherwise well cared for, but used that filter. Both are unusual situations in that the owners put 600-1000 hours a year on them, but.....they only show what will happen to your engines in 10 years. The 6022 and equivalents often do not completely seal, especially if you are using the original filter canister with old, sometimes dilapidated, neoprene. The OEM metal cased filter was a bastard size. There is an aftermarket filter made specifically to replace the 1500/1700/2000/2500 filter. $12 and change. Also available are new air canister lids, complete with new neoprene seals...app. $30. Cheap insurance.