Several consumables on a motorcycle are the most neglected. Among them: Engine coolant and brake fluid. But perhaps the most neglected item is fork oil.

But first, let's examine how forks work.

How do motorcycle forks work?

The forks' primary roles are to absorb shocks and push the tyres onto the road. Doing so allows the tyre to conform to the road's surface and thereby enhancing traction.

Forks are filled with oil these days, hence they are technically called hydraulic forks. The oil is forced through orifices to control their velocity to provide damping characteristics. Without damping, the forks will have to rely only on the springs and compressed springs will compress too quickly and re-extend past their original lengths, causing the bike to wallow up and down like a boat.

Since the oil is subjected to kinetic forces and convert these forces to heat, it will wear out. Just like the engine oil. The bike's handling will be different at first, then suffer as time goes on if the oil is not changed. (And old fork oil smells like cat pee!)

When should I replace my fork oil?

The problem is some motorcycle manufacturers don't print the recommended replacement period in the owner's manual. But those who do, all recommend the same replacement period of 20,000km. You many replace the oil with the manufacturer's recommended grade.