Standard oil and filter service on the AMC/Chrysler 4.0L straight-six. Sump holds 6 quarts with filter; use 10W-30 conventional or synthetic for most climates.
The 4.0L is famously tolerant of oil choices, but it benefits from a clean change every 3,000-5,000 miles on conventional or 5,000-7,500 on a quality synthetic. Factory fill spec is 10W-30 for most ambient temperatures; 5W-30 is acceptable in winter and is what later FSMs list. Capacity is 6.0 quarts (5.7 L) with a new filter. Renix-era (1987-1990) and HO (1991-2001) engines share the same capacity and oil specs. The drain plug is a 15mm hex on the rear of the steel pan; the filter is on the passenger side of the block, mounted vertically, and tends to drip down the bellhousing if you do not pre-fill it. Many owners run Mopar MO-090 (long discontinued, replaced by FRAM, Wix 51515, or Mopar MO-285) for tight fitment under the manifold. Run the engine to operating temp before draining for fastest, cleanest evacuation. Re-torque the drain plug to 25 ft-lb against a fresh crush washer; the pan threads are aluminum on early years and easily stripped.
| Part | Vendor | Est. price |
|---|---|---|
| Oil filter (Wix) | RockAuto/NAPA | ~$8 |
| Oil filter (Mopar) | Mopar | ~$10 |
| Motor oil 10W-30 (6 qt) | any | ~$25 |
| Drain plug crush washer | Mopar | ~$1 |
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.
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