lhb

I've researched this and found some XJs have been upgraded with LARGER filters, but for some reason my 1999 XJ 4.0 is using a smaller filter. When i got the vehicle it had a K&N HP-1002 (https://www.knfilters.com/hp-1002-oil-filter) filter installed. It definitely does NOT fit the HP-2004 or PS-2004 as is suggested on the K&N website. Any idea what's going on here?

Here is a sticker on the engine if this answers any questions:​​​​​​​

tech

Have you tried the stock filter to see if it fits ?

lhb

I'm a moron and you're right! Looks like the mechanic didn't have the proper filter last time and found a smaller one that would work. Ugh, thank you!

Randy Bobani

All that really matters is the thread size/pitch and the gasket OD & ID.

The K&N HP-1002 is 3/4-16 thread, and has a gasket OD of 2.73", ID of 2.43"
Typical 4.0L filters are 3/4-16 thread and a gasket OD of 2.79", ID 2.42"

So it's a very close match and totally compatible with the engine's filter housing.

PJB

I've been using a Motorcraft FL-1A for a while now, it's bigger and at oil changes I'm putting 6 1/2 quarts in

IJM

I think that's roughly equivalent to the Wix 51515/NAPA Gold 1515 filters I use, right?