The 6.4L Power Wagon takes 7 quarts of 0W-40 full synthetic meeting Chrysler MS-12633 (2014-2021) or MS-A0921 (2022+) — not any random 0W-40, and not the 5W-20 a 5.7L Hemi uses. Pennzoil Ultra Platinum Euro 0W-40 is the common over-the-counter match. With the spin-on filter it is a 30-45 minute job for about $70 in materials. Get the oil grade right; the 6.4L is sensitive to the MS-12633 additive package for its lifter and MDS hardware.
This is the most frequent service the truck needs, and the one most often done wrong by grabbing whatever 0W-40 is on the shelf. The 6.4L's specification exists because the engine's hydraulic lifters and cylinder-deactivation (MDS) hardware depend on the friction and shear properties of an oil that meets MS-12633. Using a non-spec oil is the kind of corner-cut that shows up later as lifter tick.
Capacity with filter is 7 quarts. Use a full-synthetic 0W-40 carrying the MS-12633 approval (or MS-A0921 on 2022-and-newer trucks). The oil-life monitor will call for a change on its own schedule, but severe duty — towing, dusty trails, lots of idling, short trips — means changing on time/mileage rather than waiting for the monitor. A practical severe-service interval is in the 4,000-6,000 mile range; highway-only trucks can ride the monitor closer to its limit. Always reset the oil-life monitor after the change so it tracks correctly.
Warm the engine briefly so the oil flows, then shut it off and let it settle a few minutes. Position the pan, crack the drain plug, and let it fully drain — replace the crush washer when you reinstall the plug and torque it to spec (do not gorilla it into the aluminum pan). The filter on the 6.4L is a spin-on; use a cap-style wrench, pre-fill the new filter where orientation allows, and wipe the mating surface clean. Lube the new filter gasket with fresh oil and hand-tighten plus the marked turn. Add 7 quarts, run the engine, check for leaks at the plug and filter, then shut down, wait, and verify the level on the dipstick.
Check the level with the truck on level ground — overfilling a Hemi can aerate the oil and upset MDS operation. Confirm the dash oil-pressure reading comes up normally on start. Reset the oil-life monitor through the dash menu. Note the date and mileage; pairing oil changes with a quick under-truck look (axle seals, drive-shaft, skid plate hardware) catches trail damage early.
The 6.4L uses an aluminum oil pan, and that is where careless changes go wrong. The M12 drain plug wants roughly 20 ft-lb (about 25 Nm) — snug, not muscle. Run it in past that and you pull or strip the soft aluminum threads, which turns a $3 crush washer into a pan replacement or a thread-repair insert. Always fit a fresh crush washer each change; a reused washer is the most common source of a slow drain-plug weep. The spin-on filter needs only a clean gasket wiped with fresh oil and the maker's marked turn past contact (typically 3/4 turn) — a filter cranked on with a wrench is how you round the cap and glue it in place for the next person. If a plug ever feels like it is fighting the threads going in, stop and chase it by hand rather than forcing it. For the rest of the drivetrain fluids on this truck, work from the full fluid-service schedule.
The change interval is also a free inspection. Wipe the magnetic drain plug — a light gray fuzz is normal, but glitter or metal flakes point at bearing or lifter wear worth investigating. Smell and look at the drained oil: a strong fuel smell or a level that reads above full on the dipstick can mean fuel dilution from short-trip or MDS cylinder wash, which shortens the real interval. A milky, coffee-with-cream look means coolant intrusion — stop and diagnose before you refill. Owners who tow or run dusty trails hard should pull a used-oil analysis ($30 a sample) once or twice to set their own interval instead of trusting the monitor blindly. If a persistent lifter tick shows up after a change, pair the next service with a code scan using the OBD-II guide to catch an MDS or VVT fault early.
| Part | Vendor | Est. price |
|---|---|---|
| 0W-40 full synthetic, 7 qt (must meet MS-12633 / MS-A0921) | Pennzoil Ultra Platinum / Mopar | ~$55 |
| Engine oil filter (Mopar MO-339 or equivalent) | Mopar / WIX | ~$12 |
| Drain plug gasket / crush washer | Mopar | ~$3 |
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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