The TJ 4.0L takes 6 quarts of 10W-30 (factory spec) or 5W-30 for colder climates. Change it every 3,000–5,000 miles with conventional oil or every 5,000–7,500 miles with full synthetic.
The AMC-derived 4.0L inline-six has been running since 1987 and it rewards consistent oil changes. The factory spec is 10W-30 conventional, but Jeep engineers used 10W-30 when most of their production went south of the Mason-Dixon line. For cold weather or extended intervals, 5W-30 full synthetic is a legitimate upgrade — it flows faster on cold starts, which is where most wear happens.
Capacity is 6 quarts with a filter change. The drain plug is on the passenger side of the oil pan, recessed toward the rear. The filter is on the driver's side of the block near the front — straightforward to reach. A filter wrench makes the initial break loose more manageable but hand-tight is the correct install torque on most spin-on filters.
High-mileage oil (100,000+ miles) makes sense if the engine is running dry between changes or if you're seeing minor seepage at the valve cover. The seal conditioners in high-mileage blends reduce seepage noticeably. Don't switch to high-mileage expecting it to fix a real leak — it won't.
| Part | Vendor | Est. price |
|---|---|---|
| Mopar OEM oil filter | Mopar | ~$8 |
| Wix 51515 oil filter | Wix | ~$7 |
| Mobil 1 5W-30 full synthetic (5 qt) | Mobil 1 | ~$32 |
| Valvoline MaxLife 10W-30 high-mileage (5 qt) | Valvoline | ~$24 |
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.