Q. I'm concerned about carbon accumulating in my car's engine block and affecting its performance. How do I avoid this?
Someone suggested not to use engine braking when travelling downhill and to use higher-octane fuel. My car is a twin-charged model. Is that good advice?
A. The best and simplest way to help stop carbon build-up is to use premium unleaded fuels. Apart from their higher octane rating, they contain special detergents that clean engines and fuel systems, which means they are a really good form of preventive maintenance.
A good run on the freeway at higher constant speed always helps dislodge carbon deposits, unless it's really caked on. In this case you will need a trip to the mechanic, where they can try a de-carb.
The engine's fuel supply is disconnected and the engine is run on a powerful cleaning agent. Carbon can set like concrete, so if all else fails the only way to get rid of it completely is an engine strip-down and rebuild.