Oil Change — 4.0L and 2.5L

The 4.0L holds 6 quarts of 10W-30 (5W-30 in cold climates) with a spin-on filter. The 2.5L 4-cylinder holds 4 quarts. Drain plug torques to 25 ft-lb, filter hand-tight plus 3/4 turn. Job takes 30 minutes.

The TJ Wrangler runs either the 4.0L straight-six or the 2.5L AMC four-cylinder. Both use a conventional spin-on filter mounted on the lower passenger side of the engine block and a 13mm hex drain plug on the oil pan. The procedures are identical — only the capacity changes.

Oil viscosity. The factory called for 10W-30 above 40°F and 5W-30 below 40°F. Either is fine year-round in most climates. Some owners run 10W-40 in hot Southwest summers — the 4.0L wears in for the long haul on anything in this range. Phoenix and Las Vegas owners can safely run 15W-40 conventional. Don't run 0W-20 — the 4.0L has wider bearing clearances than modern engines and will burn it.

Synthetic or conventional? Conventional changed every 3,000 miles or full synthetic every 5,000 miles both work. The 4.0L is an old design with loose tolerances; it doesn't reward expensive synthetic the way a modern direct-injected engine does. The exception: if your TJ has 200K+ miles and burns a quart between changes, switching to a high-mileage synthetic blend with seal conditioner can stop leaks at the rear main and valve cover.

Filter. Any name-brand spin-on filter that fits the M22x1.5 thread works — WIX 51515, Mopar 5281090, FRAM PH3614, Mobil 1 M1-110A. The filter sits at an angle on the block; expect a quart of mess if you don't position the drain pan right.

Steps

1. Run engine 2–3 minutes to thin oil. Shut off.
2. Position drain pan under the oil pan plug (rear of pan, 13mm hex).
3. Remove drain plug. Inspect the gasket — replace if crushed or torn.
4. While oil drains, reposition the pan under the filter (slightly forward and to the passenger side).
5. Spin off the old filter (counterclockwise from below). It will dump 4–8 oz of oil straight down — be ready.
6. Wipe the filter mount clean. Verify the old filter gasket came off with the filter (a stuck gasket is the #1 cause of catastrophic oil leaks after a DIY change).
7. Wet the new filter's gasket with fresh oil. Spin on by hand until snug, then 3/4 turn more. Do not use a filter wrench to tighten — that's how you crush the can.
8. Reinstall drain plug with new gasket. Torque to 25 ft-lb.
9. Add oil through the valve cover fill cap. 4.0L: 6 qt. 2.5L: 4 qt.
10. Start engine. Verify oil pressure light goes out within 3 seconds. Idle 30 seconds, shut off.
11. Wait 5 minutes, check dipstick. Top off as needed.
12. Drive 5 minutes, check for leaks around the filter and drain plug when you stop.

Why it works

• Spin-on filter is the most straightforward design ever made
• 30-minute job with hand tools only
• Cheap parts at any store
• 4.0L doesn't care about brand of oil

Trade-offs

• Filter location dumps oil on the front axle and skid plate every time
• Stuck old gasket = oil all over the driveway in 10 miles
• Owners who overtighten filters strip the threaded boss in the block (expensive fix)
• Drain plug crush gasket is often skipped — leaks slowly until it's noticed

Tools required

• 13mm socket
• oil filter wrench (76mm cap or strap)
• drain pan
• torque wrench

Parts

Part	Vendor	Est. price
10W-30 or 5W-30 conventional or synthetic blend (6 quarts 4.0L / 4 quarts 2.5L)	any API SN+ rated	~$24
Mopar oil filter (spin-on)	Mopar / equivalent	~$6
Drain plug gasket	Mopar	~$1

Sources

• AMC/Chrysler 4.0L service manual oil capacity (6 qt with filter)
• TJ owner's manual — 10W-30 above 40°F, 5W-30 below

Related

• Spark Plug Replacement — 4.0L
• Brake Fluid Flush
• All Jeep Wrangler TJ guides & tools
• Browse the full DIY database

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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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