How deterioration happens
Constant exposure to engine oil, combined with heat cycling and the mechanical stress of normal operation, gradually breaks down the rubber compound the belt is made from. Small fragments and fibres begin to shed into the oil. This process is often gradual at first — which is part of the problem, because there's usually little to notice until it accelerates.
Factors that speed it up
- Infrequent oil changes, or oil that's degraded beyond its service interval
- Use of the wrong oil specification for the engine
- High mileage, or simply age, regardless of how the vehicle has been driven
Why we recommend preventative replacement
Because visible symptoms often appear late in the deterioration process — sometimes only once debris has already begun affecting oil flow — waiting for a warning sign isn't a reliable strategy. If you don't know your belt's replacement history, or it's approaching the age or mileage typically associated with wear, we'd recommend having it looked at rather than waiting.