The ZJ takes 6 quarts of 10W-30 (4.0L) or 5 quarts (5.2/5.9L Magnum), and Mopar's MO-090 filter fits every engine option. Plan on 30 minutes if everything cooperates and the previous owner didn't overtighten the drain plug.
The ZJ's 4.0L and Magnum V8s are old, low-stress engines that don't care which name brand of oil you run — they care that you run *some* clean oil and change it on time. Use a conventional 10W-30 for high-mileage rigs that already leak; jump to a full synthetic 5W-30 if you live in Phoenix or anywhere else where the engine bakes after shutdown. Skip the heavy 20W-50 unless you're in the middle of summer and watching pressure drop at idle on a tired motor.
Mopar's 5281090AB filter (the box also says MO-090) is the OEM unit and fits the 4.0L, 5.2L Magnum, and 5.9L Magnum — one part number across the whole engine lineup. Wix 51515, Purolator L25288, and Fram TG3614 are the common equivalents. Avoid the smallest Frams; a slightly oversized filter holds more oil and is more manageable to grip when it's hot.
Park on a level surface, run the engine for two minutes to warm and thin the oil, then shut it down. Pull the dipstick to break the vacuum (oil drains faster), set the pan, and crack the drain plug with a 13mm socket. The plug is a tapered design that doesn't need a crush washer, but if yours has been overtightened in the past and weeps, replace it with a Dorman 095-002 plug-and-gasket combo.
| Part | Vendor | Est. price |
|---|---|---|
| Mopar oil filter (4.0L I6) | Mopar / Wix 51515 equivalent | ~$7 |
| Mopar oil filter (5.2L / 5.9L Magnum) | Mopar (shared filter across 4.0, 5.2, 5.9) | ~$7 |
| Engine oil — 10W-30 conventional or full synthetic | Valvoline, Mobil 1, Pennzoil | ~$25 |
| Crush washer for drain plug (optional) | Dorman 095-002 | ~$2 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.