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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 12-02-2011, 09:37 AM
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microswitch microswitch is offline
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Gas Mileage Survery

In my relentless pursuit of my 100th post I decided to post something that everyone now days strife to accomplish "Better Gas Mileage"
Years ago I was reading my gas mileage consumption on the OBC cluster and reading around 20 MPG. Then some things changed I really do not know what) and I reached 21.5 MPG. I've seen my average going down to 18 then up to 19 and now back to 17. I honestly thought with all the work I have done ( COOLING OVER ALL, VANOS ABS NEW SPARK PLUG etc etc) I would see some kind of improvement, I even got a full tank of chevron gas with TECHRON additive but nothing.
My car runs great. No code nothing. But my MPG is low. Then I notice something else.

After the reading of the gas consumption comes the average speed. Right now on my car reads 22.3 MPH and gas usage 17.6 MPG
I remember when I was averaging 20.9 to 21.3 MPG my average speed was around 27.2 MPH. So as a survey, would you report your actual OBC reading of the average MPG with the current average speed? I maybe able then to relate speed average to consumption average and look at things differently.
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Last edited by microswitch; 12-02-2011 at 09:38 AM.
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  #2  
Old 12-02-2011, 10:33 AM
jordon jordon is offline
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a higher avg speed is usually indicative of more highway travel or less stop and go, therefore better gas mileage. some other factors that can greatly affect mileage are tires (wider tires = worse mileage) and even the brand/model of tires. be sure you have a clean air filter for optimum mileage. perhaps even a differential oil change could help (fresh diff oil = less drivetrain friction = more power/better mileage). even factors like ambient temperature and elevation above sea level will invariably affect mileage. be sure you have a clean (ie new) fuel filter as well, and when it comes to injectors, the cleaner the better.
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  #3  
Old 12-02-2011, 11:47 AM
skylord skylord is offline
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Mein Auto: 99 528i M, 02 530 M
avg 44 mph, avg 24.5 mpg, my commute is about 80 miles a day, about 90% of that is highway.
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  #4  
Old 12-02-2011, 12:16 PM
Jim Rolando Jim Rolando is offline
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There are so many variales involved in gas mileage that one could drive themselves crazy trying to control all of them. But, a couple of things here; One reason gas mileage falls off at lower speed is simply inertia, you're constantly using more gas just to keep the thing rolling. Once moving at higher speed it takes less energy to keep it going at that speed. Two, if you have an automatic, the torque converter doesn't lock unti about 50 mph so you're always wasting energy with the engine over reving.

With my car running mechanically about as well as it can, I get anywhere from 18 to 22 around town, depending upon a bunch of conditions. The higher end of that took a pretty good jump when I did my CCV and stopped all of the little vaccuum leaks. On the highway I usually get between 28 and 31 depending upon how much I'm feeling like Sterling Moss that day.
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  #5  
Old 12-02-2011, 12:21 PM
cn90 cn90 is offline
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Mein Auto: 1998 528i 5-sp 140K+
I get 33 mpg when doing long trip at 70 mph.
Car is 5-speed 6-banger.
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  #6  
Old 12-02-2011, 12:52 PM
jordon jordon is offline
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Mein Auto: E39 M5, E60 530i
In my 540i6, if doing only city driving, I average about 17.5-18mpg, and I drive hard. When highway driving, I cruise at 70mph and get 26mpg.
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  #7  
Old 12-02-2011, 01:23 PM
stovey stovey is offline
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Driving an '02 530i 5-speed that's approaching 200000 miles, I see 20-24 mpg around town and about 30 on the highway.

Not uncommon to get 33-35 mpg when on paved backroads at lower speeds (55mph), which I often prefer to freeways when routing vacations.
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  #8  
Old 12-02-2011, 01:29 PM
Turbo_525 Turbo_525 is offline
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So I last disconnected my battery last June, replacing the FSU then. (Best way I know to reset OBC mileage & ave speed).

Since then 29.4 Ave Mpg; 37.5 Mph,

I have records of each fill up, and will report back when I put them into excel. Last time I did, it ranged from 26 - 33 mpg, so close to ~29 mpg ave.

525i with a 5-speed, driven "assertively" but obeying posted speed limits.
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  #9  
Old 12-02-2011, 02:30 PM
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bluebee bluebee is offline
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Mein Auto: 02 BMW 525i M54 auto 130K
- What gasoline mileage should an E39 get (1) (2) (3) (4) (5) (6) (7) (8) & the truth about mpg calculation accuracy (1) (2) & E39 great mpg stories (1) (2) (3) & E39 awful fuel mileage issues (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30)
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  #10  
Old 12-02-2011, 03:29 PM
540nj 540nj is offline
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Mein Auto: 03 540i6
driving yesterday, avg speed 75 mph, 95% hwy, 23mpg calculated at the pump. 3.15 diff.

dave
03 540i6
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  #11  
Old 12-02-2011, 03:43 PM
ilian007 ilian007 is offline
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Mein Auto: BMW 530i 2002
I dont really take attention to the gas mileage fill it up and go
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  #12  
Old 12-02-2011, 04:08 PM
Mikes530 Mikes530 is offline
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Commute roughly 30% city, 20% highway & 50% heavily-traveled rural roads. 27 mpg (US gal) avg speed 38.5 mph.
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  #13  
Old 12-02-2011, 04:33 PM
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champaign777 champaign777 is offline
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As far as i can drive 300 miles in town and 450+ miles on a HW my MPG is perfect

Last edited by champaign777; 12-02-2011 at 04:35 PM.
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  #14  
Old 12-04-2011, 06:39 AM
Spinout Spinout is offline
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'98 540I. I set Consum1 once a year and consum2 after every tank refill.

consum1=21.0
consum2=varies although on my daily 75 mile RT commute, I ave 21.5-22mpg @ 46.3mph. On highway trips, I get 25-26.5 mpg @74.0mph.
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Last edited by Spinout; 12-05-2011 at 01:22 PM.
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  #15  
Old 12-04-2011, 11:54 AM
NZ BMW NZ BMW is offline
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Converting into US measurements I get just over 18mpg around town and the average speed of my car according to the computer is about 33km/h or about 21mi/h - I spend most of my time stuck in traffic crawling and then starting from stops.

Out on the open road I get pretty good mileage I'd say at least 25mpg
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  #16  
Old 12-04-2011, 02:06 PM
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Fudman Fudman is offline
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Quote:
Originally Posted by Jim Rolando View Post
There are so many variables involved in gas mileage that one could drive themselves crazy trying to control all of them.
Forget controlling them. Just trying to identify all of them will drive you crazy. That makes every comparison of gas mileage an exercise in comparing apples and oranges. FWIW, I get 23 around town and 30 on the highway at a steady 70 mph, which makes me happy as a clam. Can't give average speed cuz my MID no longer has the dual input lower right button. But you can't find a 1/4 mile of flat level ground here in New England I would think my mileage could be better in the flatlands. Who knows...

Last edited by Fudman; 12-04-2011 at 02:08 PM.
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  #17  
Old 12-04-2011, 02:30 PM
Westlotorn Westlotorn is offline
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We have two E39's, 525i 5 speed manual and 530i automatic. Vanos done on both. New plugs in both, running the Champion Iridiums and really like them.
The 525i gets 5 mpg better all the time and really frustrates me. In town the 525i will be 21 plus the 530i 14.5 to 18 depending, it does get many short trips.
The HWY is closer, at 80 mph the 525i can get 32 the 530i will be 27.5. Steady 65 the 525i will be 34-36, the 530i will be close to 30.
I just installed new O2 sensors in the 530i, no change.
I think the Auto is too much for the 530i, I wish it was a manual but it is still a very nice car. The 525i is now approaching 165,000 miles the 530i is at 82,000, 2001 and 2002 respectively.
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  #18  
Old 12-04-2011, 03:51 PM
aspensilver540 aspensilver540 is offline
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Mein Auto: 1997 540i
18mpg overall, I find it hard to accurately guess city or highway. My area also is quite hilly and the freeway I always use has quite an incline on the way home. Never put new plugs in the car since i've owned it, 91k to 116k now, so that will be interesting to see if I get any boost.
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  #19  
Old 12-05-2011, 09:34 AM
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microswitch microswitch is offline
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Thank you for your reply.

So far I was able only to ascertain the following;

Microswtch 525 22.30 MPH = 17.6 MPG K=.785
Sky lord 528 44.00 MPH = 24.5 MPG K=.556
Turbo25 525 37.50 MPH = 29.4 MPG K=.782
Mike530 530 38.00 MPH = 27.0 MPG K=.710
Spinout 540 46.00 MPH = 21.5 MPG K=.467
ecpfenninger 525 30.00 MPH = 28.0 MPG K=.930
doru 530 30.00 MPH = 20.0 MPG K=.666

Certainly not enough data to make a assessment but it seems like Spinout and Sky Lord have the best Gas Mileage. Will edit this post as I receive more reporting of MPH vs MPG
CORRECTION ** Spinout and Skylord have the "Worse" Gas Mileage.
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Last edited by microswitch; 12-06-2011 at 04:36 PM.
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  #20  
Old 12-05-2011, 01:21 PM
mifesto mifesto is offline
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there isnt a direct relationship between average mph and mpg. for example if you go 10 mph half the time and 100 mph the other half, you'd get around 55mph BUT you wont get nearly as good mpg as truely going around 55mph the whole trip. i have no idea why you are collecting average mph data.
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  #21  
Old 12-05-2011, 02:18 PM
bobdmac bobdmac is offline
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Originally Posted by mifesto View Post
there isnt a direct relationship between average mph and mpg. for example if you go 10 mph half the time and 100 mph the other half, you'd get around 55mph BUT you wont get nearly as good mpg as truely going around 55mph the whole trip. i have no idea why you are collecting average mph data.
I have to admit I'm kind of mystified by the point of this thread as well.
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  #22  
Old 12-05-2011, 02:47 PM
540nj 540nj is offline
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Originally Posted by bobdmac View Post
I have to admit I'm kind of mystified by the point of this thread as well.
I feel like I wasted my post... ;-(

dave
03 540i6
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  #23  
Old 12-05-2011, 03:01 PM
Mikes530 Mikes530 is offline
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Sorry Micro, you've lost me with your figures. It looks as if you've just divided the mpg by the mph to come up with K and you're saying that the lower this figure the better the mileage. Seems to me that K is simply gal/hr or burn rate which might mean something in a static engine with constant load but is meaningless in this application. What am I missing?
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  #24  
Old 12-05-2011, 03:18 PM
jordon jordon is offline
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Quote:
Originally Posted by Mikes530 View Post
Sorry Micro, you've lost me with your figures. It looks as if you've just divided the mpg by the mph to come up with K and you're saying that the lower this figure the better the mileage. Seems to me that K is simply gal/hr or burn rate which might mean something in a static engine with constant load but is meaningless in this application. What am I missing?
this
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  #25  
Old 12-05-2011, 03:18 PM
NZ BMW NZ BMW is offline
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Quote:
Originally Posted by mifesto View Post
there isnt a direct relationship between average mph and mpg. for example if you go 10 mph half the time and 100 mph the other half, you'd get around 55mph BUT you wont get nearly as good mpg as truely going around 55mph the whole trip. i have no idea why you are collecting average mph data.
I think the inference is that if you've got a lower average speed it indicates lots of stop-go traffic. It's pretty unlikely that someone drives at 10mph on a clear road just for kicks, but who knows
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