I pulled my rocker cover off a while ago and had not done an oil change for a good 8-10k of hard driving (slack ass I usually do it every 5000kms), not to my suprise the engine oil (Nulon 10-40W) was pretty black but the oil was still stuck to everything, keeping inside the spaces between the the teeth of the cam gears that where upsidedown..... the sh*t was stuck to everything. I had to get some work done later and pulled the rocker cover off again roughly 800kms after an oil change.. I found everything was clean no more black anywhere and again the oil was stuck to everything doing its job.