Originally Posted By: pitzel
Excess exposure to volatilized components through the PCV and crankcase recirculation systems, which lead to intake deposits. The first dozen or two hours on an oil is probably the worst. After that, rates slow down quite considerably.
A few years back I did a meta analysis of a model-specific enthusiast Internet forum where hundreds of people complained about problems with their specific new DI engine and the intake deposits. Everyone was changing oil far more frequently than the manufacturer's recommendation in a misguided belief that they were 'helping' their engine. And a high percentage were having said oil changes performed by dealers.
Strangely enough, the intake problems did not show up in Europe where there is not only a culture of longer drains, but maintenance providers who aren't looking to cut corners to meet a certain "low" price point (ie: a $30 oil change at a quickie lube or dealer, for example!).
Interesting theory, especially knowing that VW's that were having issues with CBU were maintained at VW on 10K schedule. Granted using Castrol 5W40 POS.