What year and engine?? I have a '07 and am getting the EPA mileage--on a recent 3000 mile trip easily 25-27MPG and 18-19 in the suburbs in the cold weather. I know the older 3.0 with 5sp auto gets less than the '07 but not that different. Have the dealer do a diagnostic on it--covered by warranty. Also gas with ethanol added will reduce mileage--It has been documented that 10% ethanol will cause 5% drop in mileage--many add more ethanol during winter to prevent icing--also found that E85(85% ethanol) will drop mileage by 30 to 40%--Since about a week ago my x3 3.0 has been getting horrible gas mileage. It's hovering around 13-14 with a mix of highway and local driving. I've tried STP cleaners but it hasn't been working, anyone got any suggestions??
Thanks for the replies guys, it's a 2004 and I just got it back from the dealer today for the check up. They said the diagnostic didn't turn up anything so I guess I'll have to wait till this tank is empty and try some other cleaners. It has 40k miles so the break in is definately not the issue. I really think it was some bad fuel, it was consistantly at around 19-20 with a mix of highway/local ever since I got the car new but all of a sudden it dropped after filling up. I'll keep everyone posted, more suggestions welcome. Thanks everyone.