I own a 2006 650i cabriolet. For more than a year, the Service Engine Soon light periodically comes on. It often comes on after filling the tank with gas and remains on for a 100 miles or so. When I talked to a dealer representative, he said for me to use the highest octane gas and also check to make sure the gas cap was screwed on tighly. I always use the highest octane fuel I can get, usually 91 octane. I always make sure the gas cap is tight, but this doesn't help. The car is still under warranty, but I have forgotten to mention the problem when I have service. Any ideas?
