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      12-09-2013, 12:12 AM   #1
dbs600
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Very Poor Fuel Economy in Recent Months

I’ve been getting very poor fuel economy for the past three months.

I’d previously get an average of 10 mpg’s, but same dropped to 8.

Service engine light came on about a month ago and the dealer replaced an oxygen sensor.

I also complained of poor fuel economy, but the repair order came back stating no problem found and that there are additional fuel additives during winter months!? Strange, as I've never had this problem before.

Still getting 8 mpg’s and exceptionally pissed with BMW's constant denial of problems when I have any; doesn’t matter which dealer I use.

What should I do? Below 10 mpg’s is just not right, and upsetting.

Thanks.
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      12-09-2013, 08:26 AM   #2
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Quote:
Originally Posted by dbs600 View Post
I’ve been getting very poor fuel economy for the past three months.

I’d previously get an average of 10 mpg’s, but same dropped to 8.

Service engine light came on about a month ago and the dealer replaced an oxygen sensor.

I also complained of poor fuel economy, but the repair order came back stating no problem found and that there are additional fuel additives during winter months!? Strange, as I've never had this problem before.

Still getting 8 mpg’s and exceptionally pissed with BMW's constant denial of problems when I have any; doesn’t matter which dealer I use.

What should I do? Below 10 mpg’s is just not right, and upsetting.

Thanks.
Wow, That's pretty low.Though I don't have my car yet,those figures are just crazy.I certainly would not be happy owning a car with those figures.Is this pure new york city driving?Did you check your tire pressure [winter]?Other owners could throw some light here.
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      12-09-2013, 06:44 PM   #3
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Quote:
Originally Posted by luvthestck View Post
Is this pure new york city driving? Did you check your tire pressure [winter]?
Probably 75% Long Island, 25% Manhattan driving.

Yes, tire pressures are fine.

Thanks though.
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      12-09-2013, 07:26 PM   #4
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Quote:
Originally Posted by dbs600 View Post
Probably 75% Long Island, 25% Manhattan driving.

Yes, tire pressures are fine.

Thanks though.
Mine are all getting about 17 miles per gallon to 20 miles per gallon. I drive mixed city/highway. I do not use the eco modes and I have the AC on always.

Maybe cold weather is a factor?
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      12-09-2013, 10:06 PM   #5
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Maybe cold weather is a factor?
Shouldn't be as the mpg dip is a new issue; car is 3 years old...?
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      12-09-2013, 10:36 PM   #6
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Well I don't care what anyone says, 8mpg is just ridiculous for a 7. Even my X5M would get better mileage than that. Something is not adding up there...
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      12-10-2013, 01:11 AM   #7
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My car just turned 3 years old and my mpg has risen from around 13 mpg to 16.6 mpg and yes they do add additives to the fuel during winter months.
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      12-10-2013, 08:01 AM   #8
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So all the dealers around say that those figures are normal.That's just so wrong.The way I see it is that you have two options.

1.Wait until winter passes and prove them wrong
2. Prove them wrong now.You could ask them to show another owner with similar mileage .
But before you go the confrontational route,Check your tire pressure,make sure you check the actual figures on a long trip on the freeway[not relying on the on board computer]. Then repeat the same act in the city and confront them with the proper figures.

If they still deny you a thorough inspection,contact their service manager by email i detail telling them about the number of times you had requested the service for the same reason etc..and get a response [proof]. Then call BMW NA and hopefully they have the brains to think properly.I have a feeling that these guys have " heck he can afford a 7 and he complains about Mileage" attitude.

And please Never ever buy a Car from these guys.
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      12-10-2013, 10:34 AM   #9
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Thank you very much for the support, Gentlemen!

And luvthestck for all the detail, which puts things into perspective!
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      12-11-2013, 10:55 AM   #10
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I'm in NY/NJ every other week. My take is NY traffic gets worst this time of the year, compared to the summer months (Holiday/Weather/More Cars). You're probably spending more time in traffic, to accomplish the same miles. 8-10mpg is about right for a big V8 moving 15mph in the city/stop and go + unpredictable traffic in LI.
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      12-11-2013, 03:48 PM   #11
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Quote:
Originally Posted by JNoSol View Post
I'm in NY/NJ every other week. My take is NY traffic gets worst this time of the year, compared to the summer months (Holiday/Weather/More Cars). You're probably spending more time in traffic, to accomplish the same miles. 8-10mpg is about right for a big V8 moving 15mph in the city/stop and go + unpredictable traffic in LI.
Car is 3 years old; has always done 10 mpg's in past, whatever season. Thanks though.
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      12-11-2013, 10:44 PM   #12
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Originally Posted by dbs600 View Post
Car is 3 years old; has always done 10 mpg's in past, whatever season. Thanks though.
Gotcha. Any change in fuel station or fuel quality in the last 3 months?
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      12-11-2013, 11:21 PM   #13
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Gotcha. Any change in fuel station or fuel quality in the last 3 months?
Nope; same throughout; Sunoco Ultra 93.
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      12-12-2013, 02:56 PM   #14
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Quote:
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Nope; same throughout; Sunoco Ultra 93.
I can't think of anything else, other than fouled spark plugs, clogged injectors, old air filters. BMW recommend that you replaceme the spark plugs every 60k miles. Turbo cars air/fuel mixture isn't perfect all the time, so 60k miles might be optimistic.
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      12-13-2013, 09:41 PM   #15
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Quote:
Originally Posted by JNoSol View Post
I can't think of anything else, other than fouled spark plugs, clogged injectors, old air filters. BMW recommend that you replaceme the spark plugs every 60k miles. Turbo cars air/fuel mixture isn't perfect all the time, so 60k miles might be optimistic.
Could a bad O2 sensor cause the spark plugs, injectors or air filters to get dirty?
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      12-17-2013, 03:19 PM   #16
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Quote:
Originally Posted by dbs600 View Post
Could a bad O2 sensor cause the spark plugs, injectors or air filters to get dirty?
Absolutely. O2 sensor helps the computer determine the right air and fuel mixture. When it goes bad, it is not sending the right voltage to the computer causing an incorrect air/fuel mixtures. This could mean a rich/lean fuel/air mixture = worst fuel econ, fouled spark plugs, carbon build up, fouled CAT convertor.

A bad O2 sensor doesn't damage the air filter.

You can have your dealer check them. There's a way for them to check the voltage output on them.
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      12-17-2013, 03:40 PM   #17
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Quote:
Originally Posted by JNoSol View Post
Absolutely. O2 sensor helps the computer determine the right air and fuel mixture. When it goes bad, it is not sending the right voltage to the computer causing an incorrect air/fuel mixtures. This could mean a rich/lean fuel/air mixture = worst fuel econ, fouled spark plugs, carbon build up, fouled CAT convertor.

A bad O2 sensor doesn't damage the air filter.

You can have your dealer check them. There's a way for them to check the voltage output on them.
Thank you very much for this most detailed insight!

Last edited by dbs600; 12-24-2013 at 09:54 PM..
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      12-23-2013, 11:18 PM   #18
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Quote:
Originally Posted by dbs600
Ive been getting very poor fuel economy for the past three months.

Id previously get an average of 10 mpgs, but same dropped to 8.

Service engine light came on about a month ago and the dealer replaced an oxygen sensor.

I also complained of poor fuel economy, but the repair order came back stating no problem found and that there are additional fuel additives during winter months!? Strange, as I've never had this problem before.

Still getting 8 mpgs and exceptionally pissed with BMW's constant denial of problems when I have any; doesnt matter which dealer I use.

What should I do? Below 10 mpgs is just not right, and upsetting.

Thanks.
Okay, I completed the test. I am getting really crappy highway gas mileage: 14 miles per gallon.
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      12-25-2013, 12:49 AM   #19
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Okay, I completed the test. I am getting really crappy highway gas mileage: 14 miles per gallon.
I'd love to be getting 14 mpg's.

Never have once. :|
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      12-27-2013, 10:14 PM   #20
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Wow, that is very strange. You should not be getting 8-10 mpg. I recently sold my 2010 750i which I drove 90% of the time in a city which has extremely high traffic. I never got below 13 mpg.
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      01-14-2014, 12:16 PM   #21
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Wow... that's abysmal MPG. I live in San Francisco and commute about 45 miles each way to work. 40 miles of highway, and about five miles of surface streets, and have been averaging MPGs in the mid-20s -- generally 23 to 25mpg. This is precisely the reason I chose the 740Li over the 750. The 750's turbo-8 is phenomenal, but the frequency of refueling would drive me crazy. I fill up once a week. Time is money
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      01-16-2014, 08:57 PM   #22
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Quote:
Originally Posted by TheBry
Wow... that's abysmal MPG. I live in San Francisco and commute about 45 miles each way to work. 40 miles of highway, and about five miles of surface streets, and have been averaging MPGs in the mid-20s -- generally 23 to 25mpg. This is precisely the reason I chose the 740Li over the 750. The 750's turbo-8 is phenomenal, but the frequency of refueling would drive me crazy. I fill up once a week. Time is money
Yep, time is money.

My 750Li Xdrive gets me to work 20 minutes faster than your 740.

40 minutes per day x 260 days = $lots of dough!
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