Normal vs. Abnormal Results

How can we tell if something’s not right? We compare to averages and compare to the trends you’ve established.

For example, we do a lot of BMW M3 samples from owners who are concerned about bearing wear. Below are side-by-side samples of a normal M3 and one with poor bearing wear.

Both are 2003 M3’s with the S54 engine. Both have 5,000 miles on the oil, and both are running 10W/60 oil. Lead is just 8 ppm in the sample on the left, and 37 ppm in the one on the right. The engine on the right is suffering from poor bearing wear.

We have averages for most types of systems, and even if we’re seeing something new, we probably have a pretty good idea of how it should be wearing. We take into account things like shorter or longer oil changes, hard use, inactivity, contamination, make-up oil, and the zillion other factors you tell us about. Sometimes we’re stumped about whether something’s out of line…but usually we’re not.