Hybrid vehicles have gained popularity in recent years due to their fuel efficiency and environmentally-friendly features. However, these vehicles tend to build up more carbon deposits in the engine compared to traditional internal combustion engine (ICE) vehicles. This is due to the irregular engine start and stop characteristic of the hybrid vehicle system, which results in a specific amount of unburnt fuel turning into carbon deposits left in the combustion chamber in every cycle, repeatedly.

Over time, carbon deposits accumulate in various areas of the engine, including direct fuel injectors, intake and exhaust engine valves, and spark plugs. Such deposits also clog the catalytic converter in the exhaust system, leading to erratic engine idling. This, in turn, causes catalytic converters to overheat because of excessive amounts of unburnt fuel. In extreme cases, this may trigger engine fault code P0420, which stands for Catalyst System Efficiency Below Threshold (Bank 1). A failed oxygen sensor in the exhaust system can also cause overheating.

Furthermore, engine performance may respond sluggishly or even stall while cruising or in traffic jams, which can be frustrating for drivers. To mitigate these issues, using a fuel system cleaner such as Cataclean can prevent erratic engine idling due to fuel injector fouling from the irregular engine start/stop condition of hybrid engine systems. This cleaner also reduces carbon deposit build-up in engine valves and the catalytic converter in the exhaust system, thus improving the overall performance of the vehicle.