Coming from the days of 3 months or 3,000 miles the long intervals make me a bit nervious. For a little piece of mind, I sent the oil off at the last change for a UOA. Car (2000 E38) had 122,220 when sample was taken. I know a lot of us use the LL01 0W-40 Mobil 1 so I thought it would be of interest. FYI, combination of city driving and short freeway runs. My average MPH since I bought the car only shows 26MPH! Shoot, the file is to large (137k) so here is the long and short of it: "No problems showed up in the first sample from your BMW. Universal averages for teh 4.4L M62 are basond on an oil run of ~5,900 miles. You ran this oil a lot longer, so we are happy to see all metals reading well within the normal range, and we think that's a good sign that no problems are developing. The TBN read of 2.1 so you had plenty of active additive remaining for extra miles. 1.0 is considered to low for extended use. The oil was free of any fuel dilution or anti-freeze, and the low in solubles show good oil filtration. Try going 18,000 miles on the next oil" If you want to see the entire report, you can download it here: http://forums.bimmerforums.com/forum/showthread.php?t=1668927
UOA is a good means to tell if the oil is still serviceable. Obviously your oil was just fine as has been the case with most folks. There is a lot of concern by folks who are use to shorter OCIs but up to 15K miles has been used for many years without issue as long as you use the proper LL-01 oil. Mobil 0w-40 is the only Mobil product sold in the U.S. that meets the LL-01 specs as it is in fact a Euro formulation oil.
I was pleased with the UOA. I have seen in the motor both without an oil pan or valve covers on it and it is perfectly clean. I have had the car for about 30,000 miles and it appears that the previous owner followed the maintenence minder and had the dealer do the oil changes.
