X5 Gas Mileage

I have 2008 X5 4.8 and its been great, but recently my gas mileage has gotten horrible, even though my driving hasn't changed. I usually average around 14 MPG in the city and 20 on the highway. I live in Charleston, SC and do a lot of city driving, but about a week ago my mileage average dropedp to 15, then 13, then 11, and today 10. It continues to fall about .5 mph every few days and I am wondering if the computer is messing up or the car is burning more gas then usual or what the problem could be. I am trying to keep track of the distance I drive to see if its the computer, but the problem of bad gas mileage only happened since the last fill up so not enough data yet. Any advice, recommendations, are other people experience horrendous gas mileage.

Could be a faulty computer. But also check your tire pressures.

I average around 14-15mpg in mixed driving on my 2010 X5 4.8. Horrible! Much worse than my previous car a 2007 550i

Might not get the V8 next time around.

My average is 14 mpg.

Mine is right at 16 ... Wish it was higher but I love it

Originally Posted by eldorado01

My average is 14 mpg.

Wow, that should improve for you with some break in, or you drive aggressively. Our's is virtually the same spec as yours and gets what I consider usual driving in town and runs close to 19 mpg combined. We recently took a 400 mile highway trip and managed 25 mpg with an average speed if 72, cruise control 95% of the time.

Sounds like a computer or sensor mess up. Try using the "trip computer" to monitor it over smaller intervals. I know on mine, I don't reset the main mpg so it is averaged over 1000's of miles. If my milage all of a sudden was cut in half, it would take a long time before the overall would drop that much, and certainly not .5 per day. My trip computer is showing 16 mpg over about 1000 miles right now and overall 15.2 mpg. Also, check how many miles you are getting on a fill-up to make sure it isn't an engine problem. Check under the vehicle for a fuel line leak. My guess is that your computer is registering 0 mpg and that is why your overall is dropping so fast. What does the fuel consumption gage show on the dash? Is it showing normal activity?

My 2012 35i (2000 mi so far) seems to average about 15 - 16 mpg with mostly city driving. I haven't payed careful attention to highway mpg but as I recall it seems not much better (17 - 18 mpg). I actually noticed that the mpg displayed in the instrument cluster was stuck at 15.2 mpg for a while. I reset the trip computer and the trip odometer and seems to be acting normally again. If I do any extended driving this weekend I'll post my mpg.

I don't drive the car more than about five miles per day if that, I am trying to drive more for my investigation, I did an inspection of the car, tire pressure is good, didn't identity any fuel leaks, however I did notice a strong smell of fuel near the exhaust when the car turns on. I compared my trip computer MPG to main MPG and get about a 1 MPG difference, but my main MPG is only a 200 miles old and my trip computer MPG is only 134. I think it has to be a computer issue or a mechanical issue, I am going bring it to SA on Monday and see what they suggest.

Took the car out for a quick ride to the post office and paid close attention to the MPG gauge, it is definitely acting funny. When I coast, with no foot on the gas, at 15 mph, the MPG goes to 20MPG and then falls to 12MPG as the car slows to 10 mph and stays there till I hit around 5 mph. When I coast at 20-23 mph, the MPG gauge stays at around 30MPG, getting worse MPG as the car slows down more.

That makes perfect sense. The slower you go, the worse your milage gets at those speeds because the amount of gas being used to keep the engine running becomes constant but your miles decrease. What do you suppose the mpg is when your sitting in the parking lot idling?
I think the sweet spot for me is around 40-50 mph. Also, when I get off the interstate, I usually take it out of gear. You can coast for a much longer time because there is quite a lot of compression in the 4.8, which slows the car pretty quickly when you take your foot off the gas while it's in gear. If I have to stop though, I'll leave it in gear because it slow the car more and requires less gas than with it out of gear. (It doesn't require gas to keep the engine running while coasting in gear until you reach the lower speeds.)

Originally Posted by Pjuran

I average around 14-15mpg in mixed driving on my 2010 X5 4.8. Horrible! Much worse than my previous car a 2007 550i

Might not get the V8 next time around.

My car has the sport package with the 20 inch upgrade.The GPH is reading between 9.5 and 12 max with city driving.I am concerned about this and would appreciate any comments.

My 2012 X5 35i Prem has 700 miles on it and averages 12.5 to 13 mpg in the city if I drive it easy.
My wifes 2011 328i has 1600 miles and averages 14.5 to 15 mpg in the city.
I have decided that BMW's are simply fun to drive and not economy vehicles.

I have 2008 X5 4.8, sports package, 20" wheels ... we get 16 average

Originally Posted by 2rlake

I have 2008 X5 4.8, sports package, 20" wheels ... we get 16 average

similar setup ^^^^, but I'm at 15-16 depending on how I drive it that week.

I get about 16 mpg if I try; otherwise I think my average is between 12-14 mpg at the moment since I usually floor the throttle every time I need to pass someone.

And no matter how I drive (or maybe I just drive the same every time), I get about 350 miles out of a 3/4 tank.

19.6mpg on 87octane
22.7mpg on 89octane
24.2mpg on 93octane
all on 37 cold psi in tires

Originally Posted by rattmann

19.6mpg on 87octane
22.7mpg on 89octane

!!!!