instant replay - purchased an 01 Jeep Sport 4L 5spd, 137K mi. only 1 oil change was performed over the course of 1 yr prior to my purchase of the Jeep.
Drove it a few hundred miles; very noticeable top-end engine "tick" on cold starts; "check gauges" light & warning beep would activate on warm starts; replaced oil sending unit and changed the oil.
1st oil change - 10W-40 synthetic (not sure of brand - my bad) & 1 qt. of Lucas - not sure of oil filter brand either but i'm sure it was a cheap one - my bad again.
No "check gauges" light, warning beep or top-end "tick"
2nd oil change - 10W-30 Mobil 1 synthetic, 1 qt Lucas, NAPA Gold (1515) over-sized filter. After oil change there was a VERY noticeable bottom-end "tick" at idle (@700rpm) that was not there prior to the oil change. Probably shouldn't have done it, but I drove her about 90 miles thinking it would work itself out. Yea right, tick still very noticeable at idle. Hope I didn't screw something up!
Was advised to change oil again on the basis that non-synthetic Lucas & synthetic oil was not a good mix. Something about Lucas, being as thick as it is, messes with "advanced oil molecular technology". I'm like WTF??, seriously? Hmff, sounds somewhat believable, sort of, but whatever, I don't want to screw up my engine so 'll try almost anything.
3rd oil change - kept NAPA over-sized filter on; opted for some conventional 10W-40 Mobil 1 Super for high mileage engines. She still has that bottom-end "tick" but it's not as loud as before - I think. C'mon girl, work with me here!
Plan to drive her 100 mi or so & go from there. I'm thinking it's the oil pump because I've noticed a slight drop in oil pressure with the over-sized filter. I guess for "s#!*$ & giggles" I could change back to the stock sized filter, maybe a Wix brand, and see what that does.
anyhooz...still love my Jeep!