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      08-18-2010, 01:32 AM   #1
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Unexpected improvement in MPG?

I've had my 2011 N55 e90 for 2900 miles and today I had an unusual occurrence.

I'd appreciate your help in offering whether this was a fluke, expected, or possible part problem.

I pretty much average 23mpg mixed highway & city driving for each tank, get Shell 93 octane at the same gas station. This is very typical. If I drive more spirited, get like 21.5, more conservative get 24.
I always drive with the active MPG gauge - you know goes to 6 when you floor it and 99 when you lay off the gas.

Today I get gas at a different Shell station - same 93 octane. On my drive to work I notice that my active MPGs are much higher at the same speed in which I set the cruise... usually 25-27mpg, now reading 30-40mpg. Curious. Average 27mpg for the trip to & from work.

Is this a break in period finally over and true MPG, a fluke, did I put more gas in my tank and throw off the sensor, is my sensor messed up, is this just better gasoline? What do you think?

I don't know whether to be excited or to take my car in for service.

Of course I'll be doing a manual measurement of MPG when I fill up on gas again to confirm.

I'd appreciate your thoughts.
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      08-18-2010, 02:24 AM   #2
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How many miles are on your car? The economy definitely seems to improve from when the car is still breaking in.

By the way, those N55s are rated at pretty good fuel economy. Higher in fact than a new 328i. And substatially higher than a N54 335i, or 335is. Even more strange is the fact that the heavier bigger 2011 535i is rated at better fuel economy than a 328i or 335i...crazy!

With the huge corporate average fuel economy levies, it is pretty evident why BMW decided to develop the N55 to replace the N54.....The CAFE rating has been pretty steady at around 27.5mpg for about 20 yrs now. Well, suddenly for 2011, it has jumped up to 30.2 mpg! Manufacturers stand to face huge tariffs for every tenth of a mpg below the CAFE standard for every car they sell in the U.S. It can add up to millions and millions of dollars. You can read more about the CAFE standards in the following link:


Even the big heavy 2011 7 series with the N55 pretty much gets as good fuel economy as a N54 335i.

EPA Ratings city/hwy

17/24 2011 335is(N54)
17/26 2008 335i (N54)
17/25 2011 740li (N55)
18/28 2011 328i
19/28 2011 335i (N55)
20/29 2011 535i (N55)
14/20 2011 M3 Coupe (No wonder they are getting rid of the V8!)

Checkout the prices on that 335is ($62,175) and that M3 ($83,795!)
Attached Images
2011 Alpine 335d M-Sport 12.34 @ 110.48mph
2017 i3 Terra
2008 Black 335i Sedan. 11.11@ 129.47 mph
2008 Monaco Blue JB3 2.0 335i Coupe. 11.33 @ 132.77 mph (N54 stock turbo trap speed WR)
60-130mph: 6.95 seconds stock turbo WR (.16% slope)

Last edited by hotrod182; 08-18-2010 at 02:44 AM.
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      08-18-2010, 10:10 AM   #3
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Dont trust the computer do the math to get exact results.

Miles driven \ Gallons it takes to fill up
300 miles divided by 16gallons = 18.75 MPG
Reset your trip counter every time you fill up

300 \ 16 = 18.75 MPG
250 \ 14 = 17.8 MPG
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      08-18-2010, 10:16 AM   #4
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Make sure you're not on average MPH. I did that once. Got really excited for a few minutes. Of course, if it's fluctuating between 6 and 99 but hanging out around 30 or 40, then you're probably not on average MPH.

I don't know. Maybe someone converted it into a hybrid for you...
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      08-29-2010, 11:01 PM   #5
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I use to do around 23 mpg, now its jumped up to 26 mpg on average. I'm now at 4200 miles.
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