I have H22 with only 83000km (54.000miles) on it. When I bought it, it had 3 years old oil inside, but only 3000km ran on it. The oil was completely black, when I changet it, the new oil was black in a few miles again. So I removed the valve cover and found black film all over the cover surface. I cleaned it with some clout, it went easily out. But now I see high oil consumption (approx 1 liter per 1000km). I think that the piston rings are just fixed with the old oil. How can I clean them? Put there some syntetic oil, drive it like crazy for a while and hope that the syntetic will clean the rings? Or use some engine cleaner?