The 3.7L and 4.7L take 6 quarts of 5W-20; the 5.7L Hemi takes 7 quarts. All three are factory-spec on 5W-20 conventional — but if you live somewhere hot or the engine has miles on it, 5W-30 is fine.
The WK's three gas engines share an oil weight (5W-20 from the factory) but split capacities and — critically — filters. Pre-2008 trucks use the 5281090 filter; 2008-and-later 4.7L, 5.7L, and 6.1L engines moved to a 22mm thread and use the 4884899 filter. They are not interchangeable. Cross-reference your year before you buy.
The 5.7L Hemi has a known reputation for soft cam lobes and lifter failure (the "Hemi tick"), and oil quality matters more on that engine than on the 3.7L or 4.7L. Stick to a real filter — Mopar OE, WIX, Fram Ultra, or Royal Purple — and consider a synthetic blend or full synthetic at 5,000-mile intervals if the truck does any towing or sees Phoenix summers. The 4.7L PowerTech inherits the WJ's sludge tendency; do not skip changes past 5,000 miles on that engine.
Warm the engine for five minutes so the oil flows. Lift the front with a floor jack at the crossmember and set it on stands rated for the truck's weight (a Hemi WK is around 4,750 lbs). Drain plug is 13mm on all three engines; back it out by hand the last few turns so it doesn't drop into the pan. Filter is on the driver-side of the block — accessible from below, tight on the 4.7L, cleaner on the 3.7L and 5.7L. Oil the new filter's gasket, hand-thread it on, snug a quarter-turn past contact. Don't gorilla it.
Refill from the top (6 quarts on 3.7/4.7, 7 quarts on 5.7), run for 30 seconds, check the dipstick, top off.
| Part | Vendor | Est. price |
|---|---|---|
| Mopar oil filter (3.7L / 4.7L 2005-2007) | Mopar | ~$10 |
| Mopar oil filter (4.7L / 5.7L / 6.1L 2008+, 22mm thread) | Mopar | ~$12 |
| 5W-20 conventional motor oil (6 qt — 3.7L / 4.7L) | Valvoline / Mobil / Pennzoil | ~$28 |
| 5W-20 conventional motor oil (7 qt — 5.7L Hemi) | Valvoline / Mobil / Pennzoil | ~$32 |
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.