I recently paid for my 24 hour subscripton to the TIS, and discovered that the TIS doesn't really exist anymore. Now it is called ISTA (Integrated Service Technical Application). I really wasn't able to get much out of it and in order to "dig into it" you have to provide the last 7 digits of your VIN...kinda creepy.

Anyway, I was able to get several training manuals and SIB's that were imteresting.

One SIB that really struck me was SI B13 02 10. BMW evidently by either a special testing device, or by interrogating the computer can determine for gasoline engines, what octane level is in the fuel you have been using over the life of the vehicle, or for diesel, the cetane number of the fuel most often used.

Also, 51 is the cetane number most quoted in these "internal" documents as being required, but for most people is not readily available. It's really a catch-22 for most folks: you are not allowed to use diesel fuel additives but you must be using high cetane premium fuel or face having your poor quality of fuel being blamed down the line.