In the days before fuel injection and computer controls, particularly with certain temperamental sports cars (of Italian descent), any amount of slow driving and idling would quickly result in carbon deposits building up in the engine and on the spark plugs until the point where the vehicle would start bucking, jerking, and stalling. A good hard run would be required to clean up the deposits by getting the engine hot enough to burn those deposits off before they got too attached. Hence, the Italian tune up.
Since the dawn of the internal combustion engine, by its nature, it has had the propensity to “carbon up”. Burning fuel in less than perfect conditions in the engine’s combustion chamber results in deposits. The combustion process converts oxygen, carbon and hydrogen ideally into water and carbon dioxide. As we all know our vehicles have emission controls to deal with the less than ideal state of combustion. These emission controls help reduce the nasty byproducts of combustion that try to sneak out your exhaust pipe.
There are some byproducts of combustion that, for whatever reason, end up as solid material stuck on internal engine pieces where they slowly build up and eventually contribute to reducing the efficiency of your engine. At some point the efficiency reduction presents itself as a problem that has to be dealt with. Power loss, check engine light on, rough running, and poor fuel mileage are some of the symptoms.
These deposits are made up of many different materials not just carbon. The materials are inherent in engine oil and fuel. Even though the fuel is burned and the oil is the lubricant they do come in contact in your vehicle’s air intake tract. The oil is carried in as a mist through the crankcase ventilation system and then there is the little amount that gets by the valve seals and piston rings. Many engines also have exhaust gases coming back through the engine (EGR). The result is a gradual build up of some conglomerate of these materials. They attach themselves to the intake manifold, the intake valves and the piston and combustion chamber.
At some point the deposits become serious enough to cause noticeable running problems. The rate at which they accumulate is partially controlled by you, the owner, your maintenance practices and driving style. There is also another significant factor. Some engine designs build deposits quicker.
What can you do to reduce the rate or prevent these deposits? The manufacturer of your vehicle probably has some advice for you found in the owner’s manual. Use high quality fuel that has the necessary detergent content. Use high quality engine oil that meets or exceeds your manufacturer’s recommendations. It is both what is added to the oil (detergents) to keep your engine clean as well as what is removed from the oil (sulphur, ash and phosphates) so they cannot deposit themselves in your engine.
Keep your engine oil clean by using a high quality oil filter and regular oil changes. Short trips to the grocery store need to be interspersed with long drives out on the highway to get the engine oil hot enough to get rid of built up acids and moisture.
In most cases the vehicle manufacturer will not suggest using any deposit removing additives in your fuel system but your mechanic may recommend additives and regular intake, injector, and combustion chamber cleaning.
Many engines have a high propensity for deposit build up. We have found that when you look through the manufacturer’s technical service bulletins you will find they have procedures required to clean the engine of deposits.
I would suggest a preventive approach. Heed the advice of your manufacturer; good fuel, and proper oil and your mechanic; regular intake, injector and combustion chamber cleaning.