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2010 2011 BMW 5 Series Forum F10 BMW 5-Series (F10) Forums General 5-Series Sedan and Wagon (F10 / F11) Forum Very Poor Fuel Economy in Recent Months
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      12-09-2013, 12:13 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, 12:42 AM   #2
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Most fuels in areas having air quality issues in the states have 10% or so ethanol, and if you can find any (probably not) that are all petrochemical, that may make a difference - there is literally less stored energy when they add ethanol per gallon and it does make a difference.

The length of the trip, the outside temperature, how long you sit at idle, how you drive, who is driving, whether you have winter tires, what tire pressure your run, alignment, (and lots of other things as well) all can make a difference in the fuel economy. To get that efficiency, it sounds like you're sitting in traffic a lot. The computer would log issues if the spark plugs or wires had problems. Is there a check engine light?
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      12-09-2013, 01:17 AM   #3
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Quote:
Originally Posted by jadnashuanh View Post
Most fuels in areas having air quality issues in the states have 10% or so ethanol, and if you can find any (probably not) that are all petrochemical, that may make a difference - there is literally less stored energy when they add ethanol per gallon and it does make a difference.

The length of the trip, the outside temperature, how long you sit at idle, how you drive, who is driving, whether you have winter tires, what tire pressure your run, alignment, (and lots of other things as well) all can make a difference in the fuel economy. To get that efficiency, it sounds like you're sitting in traffic a lot. The computer would log issues if the spark plugs or wires had problems. Is there a check engine light?
I average about 50-50 highway to city driving. I understand what you're stating w/r/t possible factors, but the car is 3 years old and I'm experiencing this for the first time; always been about 10 mpg's in the past. There was a check engine light on, starting about a month ago, but the dealer has since replaced an oxygen senor, which has turned off the light...

While the car has always unfortunately gotten poor fuel economy, its recent single digit numbers are plain painful.
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      12-09-2013, 09:31 AM   #4
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Quote:
Originally Posted by dbs600
Quote:
Originally Posted by jadnashuanh View Post
Most fuels in areas having air quality issues in the states have 10% or so ethanol, and if you can find any (probably not) that are all petrochemical, that may make a difference - there is literally less stored energy when they add ethanol per gallon and it does make a difference.

The length of the trip, the outside temperature, how long you sit at idle, how you drive, who is driving, whether you have winter tires, what tire pressure your run, alignment, (and lots of other things as well) all can make a difference in the fuel economy. To get that efficiency, it sounds like you're sitting in traffic a lot. The computer would log issues if the spark plugs or wires had problems. Is there a check engine light?
I average about 50-50 highway to city driving. I understand what you're stating w/r/t possible factors, but the car is 3 years old and I'm experiencing this for the first time; always been about 10 mpg's in the past. There was a check engine light on, starting about a month ago, but the dealer has since replaced an oxygen senor, which has turned off the light...

While the car has always unfortunately gotten poor fuel economy, its recent single digit numbers are plain painful.
Hi, let's try a different approach.

I typically get 16 mpg. My old 2011 750lix got 18.

Lets do miles per tank. Fill your tank and then hit the trip odometer reset. Then when your tank gets low, fill it but jot down the precise gallons of your fill up. This way we can determine mpg without using BMWs computers.

I will do the same and we can compare results in a few days.
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      12-09-2013, 06:51 PM   #5
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Quote:
Originally Posted by BMWrules7 View Post
Hi, let's try a different approach.

I typically get 16 mpg. My old 2011 750lix got 18.

Lets do miles per tank. Fill your tank and then hit the trip odometer reset. Then when your tank gets low, fill it but jot down the precise gallons of your fill up. This way we can determine mpg without using BMWs computers.

I will do the same and we can compare results in a few days.
True; I'll try same and report! Thanks.
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      12-09-2013, 08:56 PM   #6
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Quote:
Originally Posted by BMWrules7 View Post
Hi, let's try a different approach.

I typically get 16 mpg. My old 2011 750lix got 18.

Lets do miles per tank. Fill your tank and then hit the trip odometer reset. Then when your tank gets low, fill it but jot down the precise gallons of your fill up. This way we can determine mpg without using BMWs computers.

I will do the same and we can compare results in a few days.
That's the best advice. I was going to ask how he was calculating his MPG, your way or using the BMW computer, but this way should be the most accurate.
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      12-13-2013, 09:54 PM   #7
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Quote:
Originally Posted by BMWrules7 View Post
Lets do miles per tank. Fill your tank and then hit the trip odometer reset. Then when your tank gets low, fill it but jot down the precise gallons of your fill up. This way we can determine mpg without using BMWs computers.
Thanks for the help, BMWrules7!

Part I, instrument cluster, as promised:

So on my next fill up I should divide mileage accrued by gallons poured?
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Last edited by dbs600; 12-13-2013 at 09:59 PM..
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      12-14-2013, 04:07 AM   #8
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Exactly. If you want a way of tracking this on a regular basis, I find www.Fuelly.com to be a fantastic tool, as it does all the calculation for you, and gives you a lot of data from that. And as you can easily track it over time, you can pick up any faults earlier.
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      12-14-2013, 07:57 AM   #9
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Quote:
Originally Posted by xs2man View Post
Exactly. If you want a way of tracking this on a regular basis, I find www.Fuelly.com to be a fantastic tool, as it does all the calculation for you, and gives you a lot of data from that. And as you can easily track it over time, you can pick up any faults earlier.
+1. Fuelly also gives you the option of using UK gallons, which gives an immediate 25% or so improvement in mileage.
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      12-24-2013, 11:52 PM   #10
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Thanks for the replies everyone.

Here's the second picture; took 18.505 gallons to fill up.

So where does this put me?

Or do I need to go through another tank for an accurate number?

Thanks. :|
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Last edited by dbs600; 12-24-2013 at 11:58 PM..
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      12-25-2013, 06:19 AM   #11
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That would upset me LOADS to be honest. 7.4 mpg. WOW. What is your average speed over the tank?

Good thing I don't drive a 750 then...
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      12-25-2013, 09:00 AM   #12
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I'm getting around 17 mpg on my car with 1,200 miles on it in -20F winter weather - city driving only without allot of stop and go. I'd check with a dealer
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      12-25-2013, 09:01 AM   #13
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Quote:
Originally Posted by dbs600 View Post
Thanks for the replies everyone.

Here's the second picture; took 18.505 gallons to fill up.

So where does this put me?

Or do I need to go through another tank for an accurate number?

Thanks. :|

Man it is impossible this is true or what's supposed to be, BMW has to fix your car forbya, 15 MPG will be still dismal yours is in the vicinity of less than 10!!!
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      12-25-2013, 09:23 AM   #14
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Originally Posted by xs2man View Post
That would upset me LOADS to be honest. 7.4 mpg. WOW. What is your average speed over the tank?

Good thing I don't drive a 750 then...
I think my 535i mpg is low enough at over 30mpg, (UK gallons).

The average speed is the key to whether there are issues. Remember we move to "gallons per mile" when we are idling while stationary.

I know of a 335d used in city of London which was sub 10mpg in a diesel. Nothing wrong, when out of London was typical 335d figures.

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      12-25-2013, 12:27 PM   #15
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Quote:
Originally Posted by xs2man View Post
What is your average speed over the tank?
Not sure.

Quote:
Originally Posted by Grover432 View Post
I'd check with a dealer
Dealer already gave me bs line that winter gasoline blends reduce fuel economy.

Quote:
Originally Posted by soooma View Post
15 MPG will be still dismal yours is in the vicinity of less than 10!!!
Always got 10/11 mpg's since new (winter months too), but now 8 range!
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      12-25-2013, 05:24 PM   #16
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You have trip computer in your 7 series I would assume. Reset it when you next fill up, and it will tell you all your details, like miles on the tank, average speed over the tank, the computers calculation on mpg, etc...

If your average speed is only 15 mph, then that would go some way to explaining it. If it's closer to 30-40 mph (as mine is), then there is a problem.
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      12-25-2013, 07:18 PM   #17
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I have a 535i 2011, with 46000km, and I get about 8km per litre in mixed conditions (urban/highway). I drive about 50km each day.... about 30km on highway (120km/h max speed, 160km/h for me ), and the rest on downtown traffic (less than 25km/h on average).
When I get bad traffic (for example, accidents on the highway), I get about 5 or 6km/lt. By the way, the temperature here in Santiago, Chile, is very warm on this season... minimum is 13 degree Celsius, and maximum is about 33 degrees Celsius.
I use only 97 octane fuel, and I drive almost all the time on DS or manual. D is too slow and not fun for me

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      02-14-2014, 01:13 PM   #18
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Dealer states they replaced all eight injectors and plugs.

Haven’t picked up car yet, but let’s see what result.

If improved, this isn't going to be a problem in another 3 years, is it!?

Thanks.
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      02-14-2014, 01:27 PM   #19
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Also, I understand the injectors have been through a number of revisions / redesigns.

Should I look out for any particular part numbers on the Repair Order?
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      02-15-2014, 09:02 PM   #20
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Disappointed, upset, confused and sad.

All eight injectors and plugs were replaced, but there's now some type of roughness / un-smoothness!?

Happened once when idling and felt at times after keeping on the gas, but letting up a little after gear change.

Haven't noticed a difference in mpg's either, but today wasn't a good indication for same due to the snow.

Also no 'boost' in power / acceleration from what others have reported with new injectors and plugs.
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      02-15-2014, 11:21 PM   #21
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I have had my 535i for 2 weeks after having my E39 M5 for 8 years and the fuel mileage has suffered since I drive it around in sport most of the time. Driving in comfort still feels really unnatural. I often find myself looking for the clutch all the time too. ha.
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      02-16-2014, 05:00 AM   #22
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I noticed declining fuel economy during the winter months with various cars I've owned and it's mostly due to the increase use of Ethanol in gasoline. I try to only use gas from Tier-1 providers: Sunoco, Shell, BP, or Exxon and pair that with the use of BG's 44K at the beginning of winter.

I have a lead foot, so switching to Comfort+ and changing my driving style has also increased my fuel economy as well. Now don't get me wrong, I'll nudge Chekov & Sulu for Warp every so often, but not as much during the winter.
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