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E90/E91/E92/E93 (2006 - 2013)
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  #1  
Old 02-06-2014, 08:03 PM
swa34017 swa34017 is offline
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Location: Washington
 
Join Date: Feb 2014
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Mein Auto: 2006 BMW 330i
Gas Milage Drop!

I have a 06 330i. I have owned it for about 6 months and in the past 2 months the gas milage has gone down to about 17 or 18 miles a gallon. I just changed the oil and plugs and belt and havent seen a difference at all. It seems to be running a little smoother but not better milage. It popped a code for a cam sensor and o2 sensor but went away after the oil change and I was told by my mechanic that the cam sensor could have been because of bad/old oil.

Does anyone have any ideas what could be causing the drop in gas milage? Any help would be great, I might as well go buy an x5 with this gas milage.

Help me please!
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  #2  
Old 02-06-2014, 08:41 PM
65fastback 65fastback is offline
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Location: Rocklin, CA
 
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Mein Auto: '02 540i/6, '08 E93 N54
Both the cam sensor and the 02 sensor could cause a drop in gas mileage. I would fix those issues and find a new mechanic.
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  #3  
Old 02-07-2014, 06:22 AM
Momukhamo Momukhamo is offline
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Mein Auto: 335i xdrive
I'M happy if i get 17-18 mpg lol

hmm whats your regular MPG anyways?
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Old 02-07-2014, 06:44 AM
fdriller9 fdriller9 is online now
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Mein Auto: '06 AW 330xi
There's a few things you can try.

Clean the MAF with MAF cleaner. Follow the instructions on the bottle and don't touch the wires. Wait till it FULLY dries before plugging it back in.

Remove and clean the vanos solenoids by blowing compressed air through them.

These two are easy to do and don't require much mechanical skill. The maf is held in by T20? torx screws and the vanos solenoids held in by a 8 or 10mm bolt. Both can be cleaned in under an hour.

The following is more involved but I just experienced this in my 330 and it could also be affecting yours.

Check the DISA valves. Make sure the flap is stiff when they are removed from the manifold. If it's loose, it's broken. This can affect low end torque and cause some decrease in gas mileage.

With all that being said, I average about 17 mpg in my 330xi but I have a lead foot also have an additional 300lbs to lug around for the front diff and output shafts.
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  #5  
Old 02-07-2014, 06:44 AM
fdriller9 fdriller9 is online now
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Location: NJ/Philly
 
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Mein Auto: '06 AW 330xi
There's a few things you can try.

Clean the MAF with MAF cleaner. Follow the instructions on the bottle and don't touch the wires. Wait till it FULLY dries before plugging it back in.

Remove and clean the vanos solenoids by blowing compressed air through them.

These two are easy to do and don't require much mechanical skill. The maf is held in by T20? torx screws and the vanos solenoids held in by a 8 or 10mm bolt. Both can be cleaned in under an hour.

The following is more involved but I just experienced this in my 330 and it could also be affecting yours.

Check the DISA valves. Make sure the flap is stiff when they are removed from the manifold. If it's loose, it's broken. This can affect low end torque and cause some decrease in gas mileage. The inner valve requires manifold removal and the oil separator hoses can easily break when your doing this so be prepared with spares.
http://www.bimmerfest.com/forums/sho...d.php?t=751038

With all that being said, I average about 17 mpg in my 330xi but I have a lead foot and also have an additional 300lbs to lug around for the front diff and output shafts.
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Last edited by fdriller9; 02-07-2014 at 06:46 AM.
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  #6  
Old 02-07-2014, 06:46 AM
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BostonB6 BostonB6 is offline
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Mein Auto: 2013 E93
Quote:
Originally Posted by swa34017 View Post
I have a 06 330i. I have owned it for about 6 months and in the past 2 months the gas milage has gone down to about 17 or 18 miles a gallon. I just changed the oil and plugs and belt and havent seen a difference at all. It seems to be running a little smoother but not better milage. It popped a code for a cam sensor and o2 sensor but went away after the oil change and I was told by my mechanic that the cam sensor could have been because of bad/old oil.

Does anyone have any ideas what could be causing the drop in gas milage? Any help would be great, I might as well go buy an x5 with this gas milage.

Help me please!
Winter fuel blends will cause a drop in MPG, as much as 25-30% lower.
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  #7  
Old 02-07-2014, 06:59 AM
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Zeichen311 Zeichen311 is online now
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Mein Auto: '11 335xi Sedan
In addition to all the excellent suggestions above, don't overlook the simplest of the simple: When was the last time you replaced the engine air filter?
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