Changing Your Differential's Oil

Your car's differential is not necessarily one of the most well-known parts of its inner workings, but it plays an extremely important role.

When you turn a corner, the difference in distance between the inner and outer wheels of the car means that those on the outside need to turn at a faster speed. This is because, effectively, they have further to go than the inner wheels as the car turns. With wheels on the same axle, this can cause skidding, which can ruin tyres and cause the wheels to lose grip.

This is something a lot of people aren't aware of, but luckily you don't need to be – thanks to a handy device called a differential. The differential allows the wheels to spin at the speeds they need to, independently of each other, solving the problems you'd otherwise experience.

Although the differential mostly does its job without the need for any attention from you, it does occasionally need some attention. You should replace the oil periodically to keep it working at its best, and here's how.

Use the right oil

The correct oil will be marked as suitable for use in a differential. Don't use any other kind, as you might cause damage to parts.

Lift the car

The differential is located underneath the car, so you'll need to lift it to get access. Use a jack to lift up the car, making sure it's secure.

Find the differential

You should be able to spot this fairly easily. Look for a rounded part between the two rear wheels, at or very close to the centre. If you're not sure, consult your car's manual for extra guidance.

Locate the drain

Before you do anything else, place a pan or a bucket underneath the differential to catch the old oil.

The drain bolt will be at the bottom end of the differential. Once you've located it, carefully open it and the oil will begin to drain out. Leave it until it's fully drained, and then replace it tightly.

Find the filling bolt

When you've drained the old oil, it's time to refill. The filling bolt will be at the opposite end to the drain bolt. Remove it and attach a hand pump filled with your differential oil.

Pump carefully and slowly to avoid overfilling. Your car's manual should tell you the capacity, but you can also stop as soon as it begins to seep back out.