This fluid is used only in off-road cars and rear-wheel-drive cars.
You may notice that you need to change it if you hear a buzzing noise coming from the back of your Kia when your car moves, that gets noisier when the speed increases.
This lubricant fluid is essential to keep the differential in good shape. It prevents the system from wearing away and keeps its temperature stable. The differential is a set of gears that can only be found in rear-wheel-drive cars and off-road cars. This fluid is not used for front-wheel-drive cars because the differential is built into the transmission.
In off-road cars: you need to change it every 25,000 to 40,000 miles (40,000 to 60,000 kilometers).
In light cars with rear-wheel drive: it’s recommended every 90,000 miles (150,000 kilometers).
You should always read the owner's manual to check this information.
You may notice that you need to change it if you hear a buzzing noise coming from the back of your car when your car moves, and it gets noisier when the speed increases.
If for some reason you check the fluid and see that it is very dark or you can see moisture in it, you should also change it.
The differential fluid is characterized, just like manual transmission fluid, by its SAE viscosity and API standards. You can generally find this information for your Kia in the owner's manual.
For light cars, the fluid that is generally used is either SAE 75W-80 or 75W-90. Heavy cars usually need SAE 75W-140.
A common consequence of not using the recommended fluid is the overexertion of the engine and the internal pieces of the differential, which generate more resistance to move forward.
Regarding the API standards, the fluid that is usually required is the GL-4 fluid. Newer cars may require GL-5.
The differential is the last set of gears that exists before the wheels. It is used to transmit the movement from one axis to another which is at 90°, and it allows one wheel to turn slower or faster than the other, which improves maneuverability. They may be really simple sets or high-spec sets.
In front-wheel-drive cars, this set is not used because the differential is built into the transmission. In rear-wheel-drive cars this is a separate set, sometimes built into the back axis.
You can see a picture of the main set of clogs of the differential system below.