Yeah, O2 sensor can make a big difference. I still haven't found time to take the Z4 out for an MPG run. Have to pick a day and plan a good route that will get me away from traffic and not be overly boring. The Z4 is REALLY bad with stop and go and idling. But, still, I've been getting 24-25 in typical city driving over the EPA's 18.

I want to see 40 on the back roads... at least 38!