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X5 E70 (2007 - 2013)
E70 BMW X5 produced between 2007 and 2013. Discuss the E70 X5 with other BMW owners here.

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  #1  
Old 11-10-2019, 12:56 AM
abyass abyass is offline
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Mein Auto: Bmw 528i 2010
My fuel consumption turned Out to be high after changing spark plugs. Currently i am doing 19 miles per gallon in hwy. I Am concerned what went or doing wrong? Please advise!! I was expecting 23 mpg on highways

Last edited by abyass; 11-10-2019 at 05:58 AM. Reason: X5 xdriv i35 gas mileage high 19mpg @75 mph
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  #2  
Old 11-10-2019, 02:36 AM
Autoputzer Autoputzer is online now
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Is this with an X5? V8 or in-line six? Miles? How do you determine MPG? Miles between fill-ups and fuel bought at fill-up, or from the on-board computer? How "good" is your before and after new plugs MPG data? There's a difference between "expecting" 23 MPG and actually getting 23 MPG.

If you really do have a drop in MPG after getting new spark plugs, maybe you have the wrong plugs it in.

Aerodynamic drag is proportional to the cross section area of the vehicle and the drag coefficient, and to the square of velocity. The cross section area of an SUV is much higher than a passenger car. That's the first factor working against you. The drag coefficients, as least for BMW's are similar, though. The square-of-velocity thing means that a vehicle going 70 MPH generates four times the aerodynamic drag that it generates going 35 MPH.

Because of the square-of-velocity thing, wind can greatly affect MPG at higher speeds. A 10 MPH headwind means 80 MPH of airflow generating drag. A 10 MPH tailwind means 60 MPH of airflow. Because of the square-of-velocity, a tailwind helps you less than a headwind hurts you. Going 70 MPH with a 10 MPH headwind would generate 78% more aerodynamic drag than going 70 MPH with a 10 MPH tailwind. So, a high-speed trip in windy weather, even a round trip, can lower your MPG. I used to travel to Texas a lot. Texas is windy, and the wind is usually out of the west. My MPG going west on I-10 in Texas was almost always lower than it was going east on I-10 in Texas.

The grocery store I prefer is six miles from my house. It has better stuff than Winn-Dixie. I drive down a scenic coastal highway to get there, 35 MPH speed limit and only two traffic lights (one being a crosswalk that rarely turns red at night). With Frau Putzer's X3, I can achieve 40 MPG as I pull into the grocery store's parking lot. But, on the interstate at 75 MPH, it's only good for about 28 or 29 MPG. My 535i can't touch the four-cylinder X3 on MPG in town. But on the interstate at higher speeds, the 535i matches or beats with the X3's MPG.

Last edited by Autoputzer; 11-10-2019 at 02:51 AM.
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Old 11-10-2019, 05:57 AM
abyass abyass is offline
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Its x5 xdriv i35 turbo. I used to get 23-25 mpg at 75 mpg. About right size of plugs.. i got the right plug with exact part no. WHat i doubt is about oil pan gasket leaK which i know it might be creating difference due to pressure differences.
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Old 11-10-2019, 06:56 AM
Autoputzer Autoputzer is online now
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An oil pan leak should just make a mess, not reduce fuel economy. Other possibilities are bad gas, low tire pressure, clogged muffler or catalytic converter(s), bad O2 sensor(s), bad VANOS (variable valve timing), clogged injector(s). Modern cars usually generate an OBDII error code when something's wrong with anything that affects fuel economy.

I'm pretty sure OBDII can't detect a partially clogged injector. That would cause that cylinder to run lean. The O2 sensor(s) would see excess O2, and richen up all of the other cylinders, causing low MPG. Partially clogged injectors could also cause the OBC to report artificially low MPG, since the OBC assumes that the injectors are delivering all the gasoline that the computer tells them to. (The inability to detect partially clogged injectors is a good reason to use Top Tier Gas.)

How did you determine it was getting 23-35 MPG and is now getting 19 MPG? It's possible to change the correction factor for the MPG displayed by the on-board computer. Maybe somebody with access to your car is screwing with you. I heard a story once about an owner of a new VW Beetle. He'd calculate him MPG and brag about it. So, a friend started adding gas to the tank, making the perceived MPG go up. The bragging continued. Then, the friend started siphoning gas out, making the perceived MPG go way down. It drove the VW owner nuts trying to figure out what was wrong with his car that used to get 45 MPG.

If you have emission testing in NYC, getting one might prove that something's wrong. If your MPG is low, that would usually show up as very high HC emissions.

Last edited by Autoputzer; 11-10-2019 at 07:08 AM.
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  #5  
Old 11-10-2019, 10:10 AM
abyass abyass is offline
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Mein Auto: Bmw 528i 2010
1. Recently changed tires with nitrogen filled all four
2. Usually i check MPG in every refuelling @ full tank.
3. I have recently started using injector cleaning, really dont know whether it caused the chaos.
4. I do feel response of the vehicle slight low

I am considering ur suspect on injector clog. If that so how would i clean it! ?

Vanos and all rest of the sensor would have poped out as a warning. I dont have any warnings in a my dash. Oil changed every 5k

My other bet is on fuel filter but my x5 comes with fuel pump and filter together i guess.. no sign of any issues so far
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Old 11-10-2019, 10:15 AM
FredoinSF FredoinSF is offline
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What plugs did you use? BMW's like NGK's generally.

Is this for one tank? If so, could be anomaly either with the car, traffic patterns, or the person doing the math. Maybe give it a little longer?
Is everything connected correctly? Do you have any misfire codes?
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Old 11-10-2019, 06:45 PM
abyass abyass is offline
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Mein Auto: Bmw 528i 2010
Bought Genuine Bmw spark plug high power and matched with part no as suggested. So installed exactly the same from factory.

I have been driving BMW's last 16 yrs and i know how to do the math to find the mpg.

Everything has been connected correctly otherwise would have gave code for misfire. Everything seems perfect.

I have a question, if xdrive system says a problem Would that be cause with mpg? for few weeks it was poping a warning to ask me take it to dealer to check x drive system (dsc or x drive malfunction) but when i turn off the engine, its becomes normal as nothing happened!!

Checked every corner but nothing found!!

Last edited by abyass; 11-10-2019 at 09:20 PM.
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  #8  
Old 11-11-2019, 05:43 PM
Ambia1234 Ambia1234 is offline
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My 2008 X5 is only giving me 13.2 mpg. Which plugs are best to get to where you are at rite now?
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  #9  
Old 11-13-2019, 01:09 AM
ChrisM011 ChrisM011 is offline
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Mein Auto: e70 X5d, e36 M3
Fuel mileage is affected by many things. Unless you detect a misfire (there would likely be a code) it is not likely to be a spark plug. Check for vacuum leaks/boost leaks. I am unfamiliar with the 35i engine but most higher mileage engines benefit from a new coolant temperature sensor, intake air temperature sensor, and oxygen sensors. These all tend to loose sensitivity over time and do not throw codes until well out of spec.


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  #10  
Old 11-14-2019, 09:31 PM
robinasu robinasu is offline
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Cleaner

If you are getting less mileage with the injector cleaner it might be the injector cleaner.
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