[Pierre Louis]

Clearly none of the posters have presented any scientific data or molecular mechanisms of carbon buildup.

Here is an SAE paper that finds different substances found in the fuel contribute to fouling of injectors etc.

Here is another paper comparing different compositions of fuel and different rates of deposit formation.

This paper implies that lubricating oil is not found to any significant extent in deposits, but shows how different precursor molecular chains are common and in what scale.

This paper describes the almost definite association between deposits and fuel quality:

Most testing has been carried out with metal contaminated fuel. The data show that the level of deposit is fuel dependent for both base and additive treated fuel.

Finally, here is a paper that discovers that the level of fuel oxygenation may indeed affect the quality and quantity of soot formation:

Results show that increasing fuel oxygenation produces lower in-cylinder and engine-out soot levels, consistent with existing studies of the effects of fuel oxygenation on soot emissions from diesel engines. The intriguing new information is that increasing the level of fuel oxygenation produced soot with less graphitic structure and correspondingly higher reactivity. Hence, diesel fuel oxygenation may help curtail soot emissions by enhancing soot reactivity and oxidation rates as well as by preventing certain fuel carbon atoms from participating in reactions that form soot.

PL