Most of these products contain ethanol which does to some extent dissolve the carbon. You can buy products from most motorist centre that will do the same and contain ethanol. the worst problem with our engines is that most of us do not uses the cars daily, so we have a build up of carbon in the injectors which restricts the flow of fuel to the engine. To counteract this I have always resorted to using 98 Ron petrol on every 3rd fill up, as 98 Ron petrol contains more ethanol than ordinary 95 Ron Petrol and will help to keep the injectors clean. Carbon deposits on the piston crowns and in the engine combustion chambers are not quite as bad, although they do look unsightly when you take the engine apart they are not necessarily cause for major concern. In the past we used to advocate polishing and porting cylinder heads to increase the flow of gasses through the engines. Trouble is polishing and Porting an engine head is expensive and the effects do not last long on a road going car. The carbon will still build up internally as I have found out.
Mike
