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Poor gas mileage on my BMW xdrive

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I have a BMW 328i xdrive 2014 with 29,000 miles. I have noticed inaccuracies with the mileage displayed on my onboard info and I am concerned about the vehicles gas consumption. For instance, I work 4 miles from my home. I get to work as early as 6:30 am and there is virtually no traffic during my travel at that time of day. My ride is normally a smooth one with virtually no stops. However, my onboarding info shows that I travel 8 miles to work. While I understand that the numbers displayed are estimates I am concerned about the inaccuracy. Also, I noticed black soot deposits in one of my tail pipes but the check engine light has not come on. I took the vehicle to the dealer and they say there is nothing wrong with it. The estimated gas mileage for the vehicle is 23 city /33 highway and the onboard info shows my average gas mileage at 20. The speed limit on my drive to work is 40 miles and I usually have my car set at ECOPRO. Interestingly, my driving is not exclusively in the city because once a week I travel 50 miles on he highway to teach a class and every two weeks I travel 150 mile to a nearby city to visit family. My sense is that at the very least I should get better gas mileage than the 20 miles displayed on my onboard info. Any thoughts, ideas, solutions and should I be concerned?

Well, for the good news, your X3 is not out of the normal range of mileage. According to the EPA, your BMW is rated at 21 MPG city when using premium fuel. Short trips are usually “City” mileage regardless of the driving type. You should get better mileage on the longer trip, and you can easily check it. But forget the BMW trip computer. Just fill up before you leave until the gas pump “clicks.” Then, after your trips is complete, fill up again the same way. Divide your miles driven over that span by gallons consumed. Use Google Maps to plot your route if you doubt the odometer. Trip computers are tricky and what they are telling you regarding fuel economy is not always what one might assume. Double check the manual to see exactly what your particular screen is saying about mileage. Normally, when vehicles are tested, the mileage display is optimistic. In other words, the display usually shows a higher than true trip mileage. I can’t explain why your odometer is off so dramatically. That is a slam dunk and easy fix if the dealership simply zeros it and then drives it a route it knows the distance of (Google maps is helpful). To me, it seems as if they could be related. Aftermarket wheels by any chance? No matter how different they could be it would not explain your difference. Just curious.

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At 4 miles to work and 4 miles home , your car is not even reaching normal operating temp. That is really bad for fuel mileage. I once had a job that was exactly 1 mile from home. I had to change oil in much less than 3000 miles because it would get 1 qt overfull from fuel dilution and water condensation in the crankcase. My exhaust systems only lasted a year. As soon as I changed jobs to where I was 7 miles away, those problems disappeared.

My former Prius was all about mileage. We did not have navigation so our dash display was a bit minimal but we always got a readout of trip length and mileage when we shutoff the car. Trip said, 32.4 miles. I am not sure there was an odometer to even check? It was wife’s car. I rarely drove it. Are you saying the trip to work is 4 miles and your trip computer says it is 8? Your statement seems to imply that.
I don’t know how detailed your dash info screen is. The Prius had a big central display that said “look at me”, here is your mileage. Woohoo

The read out distance traveled should be an easy fix. As for the fuel usage the OP does not say if they are checking the miles per gallon the proper way or just using the onboard readout. The short commuter trip is going to get the worst mileage possible. Besides who buys a BMW for the gas mileage anyway?

When you buy an ultimate driving machine you are entitled to utimate satisfaction – that includes accurate readings. Your remark was unnecessary.

The readouts : miles to empty - avg speed - miles to gallon , some times they can be very close and sometimes there can be a plus or minus as to the exact numbers. Some are more accurate than others. For instance, on strictly highway driving our Volvo is very accurate but on short trips around town if I get 21 mpg it will read a little higher such as 23 mph. That is why I asked if you are checking the old fashioned way. Now if you odometer is saying you are going much farther than you really are that can be fixed.

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20 MPG seems reasonable for an average with so many short trips, your actual short trip driving may be less than 15 MPG.

Before leaving on your next 150 mile trip, reset your average MPG value so you can monitor the highway mileage without blending the two driving types.

The MPG display can assist you in improving your driving for better fuel economy, don’t expect mechanical failure if you can’t achieve the EPA ratings.

If you actually determine for a fact your mpg is lower than it should be, the most common cause is a thermostat that is opening at too low of temperature, causing the engine coolant to never reach the correct operating temperature that the engineers designed it for optimum performance and mpg. This is a fairly common problem but tends to occur more in the 5-10 year time range than at 3 years. If you’ve never had the coolant replaced, might be a good time to do that as part of your car’s routine maintenance. At the same time they can check the thermostat for proper opening temperature.

Does your odometer read accurately on the 150 mile trios? If your odometer reading are significantly off, you can’t use them to compute gas mileage.

My suggestion, fill your tank, go on your 150 mile trip and fill again. Compute your mileage on the miles traveled devided by the gallons used. Did your odometer read correctly ?

I never worry about mileage. I put gas in and when it needs more…I just stop at my local gas station and pump in a new supply. I have more important things to worry about in life.

Just because BMW used to market its cars as “ultimate driving machines” does not mean they actually are.

They’re nice cars, but they’re known to be hot messes in the electronics department.