Originally Posted By: Cujet
Every BMW I looked at around here (South Florida) had a quarter inch of sludge under the valve cover.
It seems BMW's came with "free" service/oil changes. The dealerships around here must be using the cheapest oil possible. And the owners must be changing the oil at the specified interval of 10,000 miles (or so) . These engines look awful inside.
I looked at an incredibly nice Z4 M. I was in love, until I pulled the oil cap. Literally 1/4 inch of sludge. The owner, a local doctor, was proud of his service record and that he brought it to BMW on schedule.
I just could not do it. I thought about filling the engine with synthetic and flush. But...
Based on the used oil analysis of my BMWs I believe that 10,000 miles is the maximum OCI that I would use. I generally change it at 7,500 to 8,000 miles- which is @1/2 of the service interval. The new BMWs now have a maximum OCI of 10,000 miles, so perhaps Munich has finally realized that 15,000 miles was an OCI too far...