2018-2023 Ram 1500 3.0L EcoDiesel Differential Fluid

Gear oil for the 2018-2023 Ram 1500 3.0L EcoDiesel

Every EcoDiesel Ram 1500 has a solid rear axle, and 4x4 trucks add a front differential through an electronic transfer case. Both run in gear oil. The Gen 3 engine in 2020-2023 trucks makes 480 lb-ft, and a 2020 EcoDiesel towed an 8,700-lb trailer through the Ike Gauntlet on a 3.55 rear axle, so the oil in that housing earns its keep.

Choosing between them

Lucas Heavy Duty 80W-90 (10043) and Royal Purple Max-Gear 75W-140 (01301) are different viscosity grades, and the Royal Purple is a synthetic. They are not interchangeable picks. Your owner's manual names the grade and spec for your axle, so match it. Trims also differ inside the rear housing: the 2020 and later Rebel EcoDiesel has an electronic locker and other trims have open or limited-slip units. Look up the spec for your exact truck instead of going by what a buddy runs.

What we carry

Lucas Oil Heavy Duty 80W-90 gear oil and Royal Purple Max-Gear 75W-140 synthetic gear oil. Both are for the differentials, not the transmission. These trucks use a ZF 8-speed automatic, which is a separate service.

Fitment notes

This is half-ton fluid for a half-ton axle; no EcoDiesel was sold in a 2500 or 3500. Buy enough to fill each housing you're servicing, and if you're on a 2018, confirm recall 18V556 on your VIN.

Frequently asked questions

How often should I change the differential fluid on my EcoDiesel?

We don't have a verified interval for this platform, so we won't make one up. Follow the maintenance schedule in your owner's manual. On a 2018, also make sure recall 18V556 was done, because it addressed rear axles that left the factory short on oil.

Which of these gear oils is right for my truck?

The one that matches the grade your owner's manual lists for your axle. Lucas is an 80W-90 and Royal Purple is a 75W-140 synthetic, so they are not substitutes for each other. If the manual isn't in the glovebox, call the shop with your VIN.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.