Finally heard from the dealer as to why my 08 x5 died at a stop sign. They said the sending unit to the gas gauge failed. Therefore, even though the gas gauge showed the tank was 1/4th full, it was actually empty. (I'm a little doubtful about this. There were no signs from the engine like faltering that it was out of gas. It just died. No coughing or wheezing, just dead.) Of course they had to order a part, hoping to get it back late tomorrow.