Virgin Member here. Question on bad MPG

[Canadian-boy]

HELLO BOYZ N GIRLS ! Wanna say that this site is great and have been surfin it since I bought my x5 2months ago and has helped me learn a lot about my truck. It's a bit of a learning curve coming from a life of Acura's to my first BM. I love my new baby but the gas is killing me at the moment??

So I picked up an x5 2006 3ltr- 2months ago with 104000km
Baby runs great except for bad gas mileage. im getting 23L/ 100km or for you U.S.A boyz thats 10mpg !? Yes most of my drivin is city/rural but it shouldnt be this bad?? Changed MAF sensor and secondary and have a recent code p0141 - o2 sensor heater circuit bank 1 sensor 2? I've read here that a PRE cat sensor can have this issue with bad MPG but not a post o2 sensor?(unless I read wrong)? What else could be my problem? No rough idle, no misfiring, no hesitation...etc.. But...fYI I haven't done the 100k maintenance yet. cause...well I just spent 15k and its killing me to think that I have to put MORE money into it (((

P.s I just tried tO post a pic of my truck from my IPad but website says picture too big?? I guess I'll try later from my computer cause ill have to resize the pic.

Glad to finally register and say hello ( as I was feeling like a spy just reading all the posts) loll
thanks to all and anyone that replies. Have a great weekend.