[BMWfan73]

Why does my 2015 X3 35i with 67k miles gets ~12-13mpg and my 20 year old Land Rover Discovery 2 with a 4L V8 and 197k miles gets 12mpg?

[e30lover318i]

I get 18-20mpg . You either have a problem with your x3 or your foot

[BMWfan73]

Originally Posted by e30lover318i

I get 18-20mpg . You either have a problem with your x3 or your foot

Disclosure: I do have a BM3 stage 1 tune, 91 octane on it. But the majority of the time I just cruise in comfort mode. I almost never get on the gas unless I'm getting on the highway. 85% of my driving is around town for work.

[pungo]

Something seems wrong I'm averaging 22 mpg(checked old school gallons/miles) 50% highway, 30% back hilly roads, 20% town in my 2011 35i. If your in town has lots of stop & go your mileage will suffer especially with jack rabbit starts. Getting a 4200 lb vehicle going from a standstill takes some energy.

[evilchargerfan]

so many variables


-maybe the land rover got highway driving the the x3 is all short drives around town
-the land rover was maintained better / the x3 needs some maint
-maybe your right foot indeed is heavier in the x3
-perhaps the method of calc was changed comparing one car vs the other car

* tosses hands in air *

[Senilsson]

My 2012 xdrive28i (N52) averages around 18-22 in downtown chicago and surrounding areas. Sounds like your car has an issue.

[n55david]

pretty sure my stage 2 flashed fbo x35i gets way better than that. its you or something is wrong

[Wgosma]

Originally Posted by Senilsson

My 2012 xdrive28i (N52) averages around 18-22 in downtown chicago and surrounding areas. Sounds like your car has an issue.

I drive same car, getting same MPG.

[BMWfan73]

Any ideas on where to start troubleshooting? The car seems to have been well maintained by the first owner (I'm the second) with regular service performed by a BMW dealership. BTW-what does FBO mean?

[e30lover318i]

Does your tune have a “stock mode” ? The tune is meant to squeeze all the HP’s out not the MPG’s so that might be your problem. I don’t have a tune so I’m not sure how much it would effect efficiency.

[n55david]

Originally Posted by BMWfan73

Any ideas on where to start troubleshooting? The car seems to have been well maintained by the first owner (I'm the second) with regular service performed by a BMW dealership. BTW-what does FBO mean?

fbo is full bolt on.

so I have a drop in filter, aftermarket intercooler, catless downpipe etc etc and it's tuned etc

[frisbeeguy]

Originally Posted by BMWfan73

Any ideas on where to start troubleshooting? The car seems to have been well maintained by the first owner (I'm the second) with regular service performed by a BMW dealership. BTW-what does FBO mean?

You need to look at codes that each control module reports and post that on here. Easy to do with Carly or ISTA/D. You may also want to see MPG with the stock tune....basically disabling the tune. Many possibilities for poor mpg. Bad sparkplugs, bad air filter, bad fuel filter (rare), bad/dirty fuel injectors are examples. I often see bad fuel injectors/sparkplugs as causes of poor mpg. Instead of guessing, past replacement records can help you identify which areas are problematic....the bmw dealer that sold the vehicle usually retains records. For example, if the BMW dealership replaced the fuel injectors, that can potentially be a problematic area as dealers often end up installing the wrong fuel injectors (surprising, I know, the part numbers get them confused for the N55) or improperly calibrating them, but history codes usually show this issue.

[383vett]

Remove the tune and check mpg.