Fuel Quality Determination (12 25 06)

Publication date: 2006-11-01
Reference number: 12 25 06
Supersedes refnos: 12 205 03

FUEL QUALITY DETERMINATION

TECHNICAL SERVICE BULLETIN

Reference Number(s): SI B 12 25 06, Date of Issue: November 2006

BMW:	All 6 cylinder engines with Siemens MS42 and MS43 engine management systems.
GROUP:	Engine Electrical Systems

Superceded Bulletin(s): S.M. B12 205 03, Date of Issue: August 2003

NOTE: This Service Information bulletin supersedes S.M. B12 205 03 dated August 2003.

SUBJECT

Fuel Quality Determination

SITUATION

Low power output, hesitation or other driveability complaints, especially under certain environmental conditions such as high ambient temperatures and high altitudes.

CAUSE

DME ignition timing adaptation for low octane fuel.

PROCEDURE

On a customer complaint basis only, verify condition, and then perform fuel quality determination using DISPlus/GT1 and the following path:

Function Selection
Complete Vehicle
Drive
Engine Management
In the center column select:
Symptoms
In the right side column select:
Complaints
Select Test Plan
In the test plan, DME fault memory is read, followed by the display of engine idle and mixture adaptations.
On the next "green screen" the RON (Research Octane Number) will be determined when you select "yes" and the arrow right.
At the bottom of the box the RON factor is displayed.
On the left side of the screen a table is shown which relates the determined RON factor to a specific RON value.

In the United States, the American Petroleum Institute uses the Anti-Knock Index (AKI) as its measure of a fuel's performance. This is the number displayed on the pump at all gasoline retailers and is derived from the average of the RON and MON (Motor Octane Number).

Using this method, AKI = (R + M)/2.

Use the following table to relate the determined RON factor to AKI (pump octane).

RON FACTOR TO AKI (PUMP OCTANE)

RON factor	RON value	AKI
0.0 - 0.2	98	91+
0.2-0.5	95	89
0.5-1.0	91	87

If RON factor is 0.2 or higher, advise customer to use premium grade fuel with an AKI (pump octane) of 91 or higher.

BMW recommends using TOP TIER Detergent Gasoline of minimum octane rating of AKI 91. For more information regarding TOP TIER Detergent Gasoline refer to SI B13 02 06 .

WARRANTY INFORMATION

For information only.