How is my gas mileage?

[Z4maniac]

I've a 2008 3.0i Auto (Sports Pkg) and I've been averaging about 20.5 mpg since I've had the car - which is about 3 weeks now.
I do about 60% highway and 40% really horrible downtown traffic.
Highway driving is with the top up and occasional A/C while downtown is with the top down.
On the highway I stay on a fairly steady pace ~70 ish but at times when I see an open stretch of lane I do give in to the temptation and floor the pedal but that has been rather rare.
Also, I drive in the manual override mode via the shifters on the steering (steptronic), not sure if the mileage is taking a hit because of this, I tend to go rather high on the rpms before I upshift (ohh the sounds she makes...) - any advice?

Thanks.

[ZStig]

sounds reasonable/normal

[Loogey Clapp]

That seems to be in the ballpark. I average about 23.5 but it sounds like you do a little more commuter driving and "spirited" driving than I do.

[Mirko]

I'm in the 20-22mpg with mixed driving ..

[Z4maniac]

Thanks for the replies.
I'm not doing too bad I guess.

I'll drive full automatic the next stint and report back on my mileage

[v3.0si]

i recently did a hwy mileage compairo on my own to see what some of the "functional" traits of BMW's aero package were...

pre diffusor and lighter wheels was 33.1 mpg over 447 miles ( ~ 70* f)

post diffusor and lighter wheels was 34.5 mpg over 383 miles ( ~ 75* f)

i have a manual and was really trying for economy. both tests were before the aero front cover went on; i'm sure it creates more drag than the factory cover.

i haven't tried in town though, mainly because i'm fairly aggressive with the sport button on.

[ZStig]

I got around 18mpg in my old 3.0

[txz4]

i was averaging around 23 in my old 3.0si. and about 19 or 18.5 in my M

[ANUSTART]

I average 21-23 all side roads doing 30-45 mph, 15 mile round trip. I usually have no choice than to take it easy.

[wasupdu]

I'd say 85% of my miles are highway so far this season. I installed the battery after winter storage and have pit on about 7,000 miles this year. The OBC is showing 29.4 mpg....

[jophish17]

ouch, my M gets similar mileage on roughly the same mix of city/highway. But it only did slightly better [24mpg] on a 700 mile highway trip @ 80mph recently

[taddpole]

I bought my M in Texas and drove it home to Minnesota - roughly 1100 miles.

I averaged 27 over the entire trip (99% highway) on cruise control between 65 and 80 mph.

Now I do about 50/50 city/highway and am averaging 22-24.

[Z4maniac]

Wow..some of you guys are getting really good gas mileage.

Any tips on how to drive "economical"..other than the proverbial no heavy feet?

[zubydafa]

i averaged 22.x on a cross country drive from WA to PA.

i think around town, spiritedly, it hovers around 17-18.

i think your figure sounds alright.

[AirOpsMgr]

My 06' 3.0i sees 33.6 on sustained freeway (70mph at around 90 degrees temp with approx 70% humididty); when the temps and humidity are lower, say below 75 degrees and less than 30% humidity, I see 35.3 mpg. I often use the manual mode to shift in lower rpms if I want to save gas.

When I first bought it, used with 52K on it, the best I could do was 30mpg freeway, after replacing the plugs, oil-change and a K&N high-flow air filter, I saw the numbers mentioned above.

Won't get into city mileage as there are too many variables

[zubydafa]

^impressive mileage

[ShakyDog]

3.0i 2007, get 26-29 MPG never seen anything lower than 26.

This is on the computer and with manual calculations.

Steve

[HOG4DNR]

On my M, my average is 18.5 and 95% of it is city driving.

[RADRACR]

17.5 MPG from Heavy Foot Harry, here.

[AirOpsMgr]

Do any of you check the MPGs based on temp and humidity?

Just curious if others see the same differences I do between MPG at high temp/humidty Vs MPG at lower temp/humdity (I know that higher humidty causes water to displace air, yielding less air for combustion - and of course hotter air being less dense than cool air)

I guess I just wonder how many miles you must drive for the computer to get an accurate average when sustaining a speed; I assume the ECU adjusts for some, but wonder how long it takes to do so..... maybe I'm getting too technical here.

[Shipkiller]

We ///M cars need to shy away from posting our mileage numbers. He has an si and the figures will be way different.

Make sure you are resetting the trip computer after each tank and do the figures manually yourself (the most accurate way).

AirOpsMgr and shakydog has what I consider realistic numbers, but this does not take into consideration there/your driving style.
On my Roadster (with steptronic automatic), I get anywhere from 25-33MPG. I would think you would also, so I think your numbers are a little low.

I also had some fuel efficiency issues on the Roadster about three years ago. My numbers were down around 22-24 MPG. No codes were reported. Troubleshooting discovered that both upstream O2 sensors (the ones closest to the engine) were bad. After replacing, my numbers jumped way up.
The only way to diagnose this is with professional equipment or an aftermarket ODB-II reader hooked up to a laptop so you can monitor/graph the voltage levels of the those two O2 sensors (B1 and B2 sensors).

The O2 sensors are supposed to run between .2V and .9V with the (crosscount) midpoint at .45V.
Mine were running between zero (0) and .4V telling the DME that the engine was always lean, so it was dumping more fuel into the combustion chambers. I was able to watch this dynamically on my laptop.

TopGear tech tip:
One thing, when/if/maybe you do buy new O2 sensors, BEFORE you leave the store, make sure you MARK which one is for bank 1 (B1, cylinders 1-3) and bank2 (B2, cylinders 4-6). They are different part numbers and are NOT marked on the box.....

[santov]

Originally Posted by Shipkiller

TopGear tech tip:
One thing, when/if/maybe you do buy new O2 sensors, BEFORE you leave the store, make sure you MARK which one is for bank 1 (B1, cylinders 1-3) and bank2 (B2, cylinders 4-6). They are different part numbers and are NOT marked on the box.....

This is awesome info. Thanks for sharing. I'm a little tempted to change my O2 as a preventative maintenance, but dang they're expensive. Plus my mileage seems to be about average. No lights or other symptoms.