A: The 4.0L changed filters at some point ('91 to '93ish) from a 51626 (metric thread http://tinyurl.com/o5qc6 ) to 51085 (std thread) to match the Mopar fleet. A 304 CJ should use a 51258 (along with most other AMC V8s). http://wixfilters.com/filterlookup/index.asp There is more to a filter than just the Oring and thread size! If you go to an oversize filter, I suggest you also prefill it (so the motor isn't running dry on startup) and get one with an anti-drainback valve (ditto) Hopefully no-one else will have the heartache of a customer we had last week who built a new AMC motor and had a Fram collapse (he dutifully changed it but didn't know chunks of it were jammed inside the oil pump outlet) in less than 100 miles, making his engine an EXPEN$IVE PO$. From: msproviero@xxxxxxxxxxx Subject: Re: [AMC-List] best oil filter for a 390? To: amc-list@xxxxxxxxxxxx Message-ID: <070420060817.4633.44AA24290001481C000012192200737478019D0A0790019D9F9C03@xxxxxxxxxxx> I use an oversize Mobil1 filter on everything. Just pulled the stock application off the shelf and matched the thread/diameter with the biggest one there. To be honest, my CJ hasn't run in so long that I forget whether the 304 I swapped in shares the same filter thread/diameter with the 4.0. Anyway, FYI the big Mobil1 MI-301 fits the 4.0. If the 4.0 is the same as the V8's (and 258's), there you go. I'm out-of-town right now, or I would go out in the barn and verify. Before I switched to synthetic in everything, I used Wix. I had the opportunity to witness a Wix cut open next to a Fram by the Dana salesman at a parts store I worked at in high school. http://www.greatlakes4x4.com/showthread.php?t=4097 http://www.greatlakes4x4.com/showthread.php?t=4101 -Spro _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today - it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/ _______________________________________________ AMC-List mailing list AMC-List@xxxxxxxxxxxx http://www.amc-list.com/mailman/listinfo/amc-list or go to http://www.amc-list.com