I think that this 'don't use synthetic oil until your BMW bike has done 20k or so miles is just a massive urban myth!
Here's why:
Assuming proper grade, decent quality and cleanliness, all engine oils that any of us are likely to put into our bikes work pretty well.
So, if oils work well (and I suggest that for practical purposes they are all as 'slippery' as each other), how does engine wear occur?
Firstly, wear occurs on start-up, when much of the oil has drained from the bearings and wear surfaces. In the initial turns of the engine before the oil has circulated, wear rates are at their maximum.
Secondly, wear occurs when the mechanical/physical effects exceed the lubrication scope. For example, if too thick oil is used, the oil cannot be drawn into the pump at a sufficient rate to supply the engine (esp when cold). Another example might be if the engine is reved so fast that the oil centrifuges from the main bearings to the big ends leaving the mains starved and under high load. (This is a big problem with the old 'A'-series engine). Finally, God knows how much oil is circulated if a bike is dropped on its side when the engine is still running!
Thirdly, engine wear occurs when the oil, itself, fails. Oil failure might occur because of contamination, overuse (the polymer chains break down) or overheating.
I can't really imagine why anyone would want to accelerate the wear on their engine. OK, you might say that you want to reduce the oil consumption. But surely oil comsumption from blow-by increases as wear increases? Even if that's not the case, I'd prefer to throw in more oil when the engine is young - and have it last, say, 200k miles, than deliberately accelerate its youthful wear but have it shagged at 100k miles.
So I have used fully synthetic from the first time that I did the oil change (12k miles - dealer serviced before then).
Finally, Mobil say of their oil: "Mobil 1synthetic motor oil outperforms conventional motor oil. Historically, conventional oils lack the performance of synthetic oils in the areas of low-temperature oxidation stability. Mobil 1 also provides superior high-temperature stability and protection against deposits. These attributes translate directly into less engine wear and longer engine life." (my emphasis).
I vote for longer engine life!
Greg
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