It could be that you have a faulty Speedo. if it helps you in some way my 89 730 does it in 8 sec and it's an Automatic which has done 120K. It was done with an almost empty fuel tank to increase the speed also it was at night and was almost at sea level which I believe plays a factor in doing this test Don't ask me why but it does according to a posting on a BMW news group hope it helps Kenny B 89 730SE