How to Buy the Right Differential Fluid

Aaron Richardson

March 20, 2025

4 min read

Aaron Richardson

March 20, 2025

4 min read

The underside of a vehicle on a shop lift, with a fluid transfer hose connected to the differential. — A fluid change kit is handy and more economical than buying all the parts separately.

This guide helps you decide which differential fluid to buy, explains the difference between differential and transmission fluids, and outlines costs to replace your differential fluid. We also recommend which parts to swap when you change your differential fluid.

Differential fluid is also referred to as differential oil and sometimes gear oil. There are multiple formulations of differential fluid for different applications. Just like engine oil, they differ in weight and additives depending on the type your vehicle uses.

The manufacturer may specify a certain type of fluid. It also makes a difference if your vehicle has an open differential, a limited slip differential, or a locking differential. Finally, make sure you know how many differentials your car has and which wheels put the power to the ground. Find these details in your owner’s or repair manual.

In a front-wheel drive vehicle, the differential is part of the transmission. The differential and transmission fluids are the same.
In rear-wheel-drive, all-wheel-drive, and four-wheel-drive vehicles, the differentials are separate from the transmission. They use different fluids.
In a four-wheel-drive or all-wheel-drive vehicle, there are up to three differentials to maintain. Each differential might specify a different type of fluid.

Two Types of Differential Fluids

Two quarts of Land Rover electronic differential fluid, displayed on a workbench. — When in doubt, go with OEM-branded fluid.

There are two basic types of differential fluid: mineral (also referred to as conventional) and synthetic.

Mineral differential fluid is made from a crude oil base, while synthetic fluid is a man-made chemical oil. Mineral oil is cheaper than synthetic differential fluid but generally does not perform as well. It’s fine to mix mineral and synthetic differential oil in a pinch. A full flush is not necessary.

Synthetic fluid can be formulated for a variety of driving, load, temperature, and other environmental conditions. It is often required in high-performance, heavy-duty, or specialty applications. For example, if your car has a limited-slip differential, it requires a different formula than a car with a regular open differential.

First things first: Consult your repair manual to confirm the type of fluid recommended for your vehicle.

How much does differential fluid cost?

Conventional fluid should cost around $10 to $15 a quart, depending on brand. For high-quality synthetic differential fluid, expect to pay between $17 and $30 per quart.

You can choose between store-brand, name-brand aftermarket (for example, Mobil 1, Motul, and Valvoline), and manufacturer-branded differential fluid. The most important thing is to get fluid that meets the criteria specified by your manufacturer. When in doubt, go with OEM-branded fluid.

If a car has one differential, it probably only needs a quart or two of fluid. A simple drain and fill usually requires one quart, but a full flash needs more. For cars with two or three diffs, you should double or triple that amount.

Replacing or flushing differential fluid as a DIY project lets you avoid shop labor, which could be between $150 and $250.

Related Parts, Tools, and Kits

An inexpensive differential fluid pump displayed on a white background. — Differential fluid pumps start at under $20.

Replace the differential plugs and washers at the same time as the differential fluid. This is good insurance against leaks and adds only a few dollars to the job. If your differential has a removable cover, now is a great time to replace the differential gasket or reseal the cover with an adhesive gasket maker.

Differentials are often in awkward-to-reach places where it’s tricky to place a funnel. We recommend buying a differential fluid pump when you buy fluid. The best examples are simple hand pumps that screw onto the fluid bottle and have a length of hose to reach the fill hole.

eBay sellers also offer differential fluid change kits, both for specific vehicles and general fluid replacement kits. The kits contain a few quarts of differential fluid, a gasket, and a gasket maker. They often also include a differential fluid pump.

If it’s your first time doing the job, a fluid change kit is handy and more economical than buying all the parts separately. Just make sure the kit contains the right fluid and gaskets for your application.

About the author

Aaron Richardson

Aaron learned early on that it's easier to be decent at a bunch of stuff than great at one thing, which led neatly to a career as a writer. He has been an automotive writer, a newspaper editor, and a business reporter, and has always worked on his own cars and bikes. When he isn't writing stories, he's wrenching on a '74 BMW 2002 or riding a motorcycle.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.