Wet belts (belts that run inside the engine oil) rely on clean oil of the correct specification to stay stable over time.
When oil becomes contaminated, the wrong oil spec is used, or service intervals are stretched, the belt can start to break down. As the material deteriorates it may:
– Soften (loses strength)
– Swell (changes size/shape)
– Crack (surface damage that spreads)
– Fray (fibres/edges start shedding)
Driving habits can play a part too. Short trips and lots of cold starts can increase moisture and fuel dilution in the oil (because the engine doesn’t always get hot enough for long enough), which can accelerate contamination.
Takeaway: Wet belts are more sensitive to oil quality and correct servicing.
