Very poor MPG! It drops during idle too...

[Bullitt]

After a short drive, I witnessed the MPG reading drop while parked with the engine on at idle. The number dropped 0.1 MPG every 30 or so seconds:
14.0..................13.9................13.8.... ..............13.7................13.6...

In light of these numbers, I've actually been driving very conservatively for the past few hundred miles just to see how good my MPG can be. If anything, I'm hoping it's just a case of a malfunctioning MPG display.

Ever since day one, my 135i has exhibited poor MPG readings. Driving conservatively has not improved my MPG numbers. On the other hand, what's odd is my MPG isn't much lower when I drive aggressively with numerous WOT's. I do reset the MPG display occasionally.

I had a high-pressure fuel pump problem which was replaced earlier this summer, but I'm not sure if this is relevant information because my MPG numbers were the same if not slightly better with the original defective pump.

What is up with my 1er? Hope it's not time to take it back for service...

[yourfriend]

i feel like whenever the engine is on, it will register the no movement as 0 mpg and caluculate the average along with that.

correct me if i'm wrong though.

[clived]

Of course it drops during idle! You're still burning fuel (so the "g" is going up) but you're not moving (so the "m") stays the same. so "m" per "g" obviously goes down......

[arrutled]

Your manual advises you to shut off your car if you think you will be idle more than 10 seconds. dont quote that, but its in there somehwere

[Lester]

Originally Posted by arrutled

Your manual advises you to shut off your car if you think you will be idle more than 10 seconds. dont quote that, but its in there somehwere

I did a search on the word idle and seconds, the only thing that comes close is the warning light for comfort access that tells you "the fob is not in the car, if the engine is turned off it will only start up again within 10 seconds".

[instantexpert]

It's all going to depend on where/how you drive. If you're driving in a city like Chicago with lots of stoplights and congestion, I'm guessing 13MPG isn't unreasonable. My E46 330i gets about that. If you're driving freeway, you should be getting closer to 30 and suburban "city" tends to be 20ish for me.

So, to answer your other question, it depends on how recently you reset the MPG meter. If you let it go for long enough then the overall fuel economy average reported will not change at a stop light because there is enough data to buffer that time. If you reset the meter a few miles before the stop light, you're definitely going to see change because the stop light is a much greater percentage of the recorded time and will, thus have a greater effect on the current number.

Nothing you are describing is necessarily out of the ordinary.

[jrc]

Originally Posted by Bullitt

In light of these numbers, I've actually been driving very conservatively for the past few hundred miles just to see how good my MPG can be. If anything, I'm hoping it's just a case of a malfunctioning MPG display.

Coincidentally, I have also been driving conservatively for the past couple of tanks just to see how the car (135MT) does. I have about a 30 minute commute each way, about 20 minutes of it at about 65 - 70 mph and the other 10 minutes 25-45 neighborhood, stop and go etc. My current average for 3 tanks is 25.2 mpg, which I'm pleased with.

I haven't gone to extremes (like turning engine off after 4 seconds as per the OM), but I have utilized a few techniques that were counterintuitive to me compared to doing this exercise with past cars. For example, if I was going for high mpg in previous cars (manual) I would always have coasted to stop lights in neutral. Someone on this board pointed out that the 1er is actually more economical when left in gear with foot completely off accelerator as gas is completely cut off that way. And it's true--using that technique the instant mpg read out is 99.9mpg, while coasting in neutral is lower.

On teh other hand, I'm sure that when I finally get this car out to the track, the average will be well below 10mpg--probably 6-8 I'm guessing. Oh well

[jrc]

Originally Posted by Lester

I did a search on the word idle and seconds, the only thing that comes close is the warning light for comfort access that tells you "the fob is not in the car, if the engine is turned off it will only start up again within 10 seconds".

It's page 99 of the manual. It's 4 seconds, not 10. That page also addresses fuel interruption when coasting in highest gear.

[pit1]

I would expect your numbers to be a little higher than that. Although instantexpert makes a good point, but your 135 should sip a bit slower than his 330 ZHP.

Are you manual or auto gearbox? What type of driving? What do you consider "conservative?"

I average 21mpg, that's a mixture of about 75% stop and go traffic 25% rural roads. I drive to conserve quite a bit, but no day is without a few punches around corners and highway merges.

I would try two things 1) reset the system before a long freeway cruise (you should average high 20's, cruise control should get you near 30mpg.) 2) don't reset after that and go back to your daily driving, take a look at the average at the end of the week. hopefully hovering around 20. If not, have it checked out.

[sunking420]

I'm getting 22-23mpg without thinking about my driving at this point. That's being normal most of the time, and having a little fun here and there. Figure 22.5 mpg with a 300hp/300lb torque twin turbo charged straight six 3.0 liter, compared to my last car, Acura RSX-Type S, 2.0 liter v-tech 4 cylinder which got 26mph. I'm happy with losing 3.5 mph. The torque alone was worth it.........

[Tom K.]

Originally Posted by Bullitt

After a short drive, I witnessed the MPG reading drop while parked with the engine on at idle. The number dropped 0.1 MPG every 30 or so seconds:
14.0..................13.9................13.8.... ..............13.7................13.6...

What is up with my 1er? Hope it's not time to take it back for service...

When you are idling, you are getting zero mpg, so the cumulative reading will drop.

Have you calculated your real mpg over a number of tanks by dividing miles travelled by gallons of gas burned (after checking and correcting for any odometer error)? Although the OBC on my 128i is accurate within 1%, I've had other BMWs with mpg readout errors approaching 10%.
Tom

[Joraq]

My mpg reader is appx. 1 mpg off most of the time.. I have loved messing with this feature and my driving. I am averaging close to 24 of mostly highway and some city driving. My highway cruises are usually around 70-80. I do not reset the computer unless I fill up.

I recommend you reset it when you fill up and don't reset it until you fill up again. Calculate the mpg yourself by obviously dividing the total miles into the amount of gas you filled the car with. Idling does kill mpg and if you want the most efficiency turning your car off at stops longer than 10 will help. I have tried most of the "hypermiling" stuff that another person mentioned awhile back and it works. Google or searh hypermiling on this forum and you'll find lots of tips.

I have also seen my car get better gas mileage with more miles.. Now, at around 6800 i'm getting close to 24, as mentioned. If you hammer it, the returning mpg will hammer you. Moderate driving will yeild moderate resutls. Overall, the car does pretty well considering.

J.

[Bullitt]

Originally Posted by pit1

Are you manual or auto gearbox? What type of driving? What do you consider "conservative?"

It's a manual. By conservative, I mean accelerating slowly, keeping RPM's below 3-4K, shifting to the highest possible gear ASAP, and not speeding. I should note that I have been driving less on the freeway lately--about 15-20% of the time, but I have purposely avoided punching the throttle to see higher MPG numbers.

I would try two things 1) reset the system before a long freeway cruise (you should average high 20's, cruise control should get you near 30mpg.) 2) don't reset after that and go back to your daily driving, take a look at the average at the end of the week. hopefully hovering around 20. If not, have it checked out.

Thanks, I will try this. Now you have me wondering if cruising on the freeway is the only way to achieve respectable MPG numbers on the 135i.

[Bullitt]

Originally Posted by Tom K.

Have you calculated your real mpg over a number of tanks by dividing miles travelled by gallons of gas burned (after checking and correcting for any odometer error)? Although the OBC on my 128i is accurate within 1%, I've had other BMWs with mpg readout errors approaching 10%.
Tom

It's time to do this.

Originally Posted by Joraq

My mpg reader is appx. 1 mpg off most of the time..
...
I recommend you reset it when you fill up and don't reset it until you fill up again. Calculate the mpg yourself by obviously dividing the total miles into the amount of gas you filled the car with. Idling does kill mpg and if you want the most efficiency turning your car off at stops longer than 10 will help.

If you hammer it, the returning mpg will hammer you.

I'm not so sure--driving like a maniac has not yielded lower numbers than what I'm seeing now. And I drove like one right after break-in. It seems like simply driving on local roads will reduce MPG drastically for the 135i regardless of driving style. For instance, in first gear acceleration from a stop, I noticed the instant MPG reading (not the overall one) is always at 6.0MPG whether I'm feathering the pedal or gunning it. Isn't this abnormal?

[windmaker]

Originally Posted by pit1

I would try two things 1) reset the system before a long freeway cruise (you should average high 20's, cruise control should get you near 30mpg.) 2) don't reset after that and go back to your daily driving, take a look at the average at the end of the week. hopefully hovering around 20. If not, have it checked out.

Thats what I usually get. I get 32 on the highway (speedlimit) and in city I get around 18-22.

If you still have the problem, maybe tell them to reset the pc for you?

[windmaker]

Originally Posted by pit1

I would try two things 1) reset the system before a long freeway cruise (you should average high 20's, cruise control should get you near 30mpg.) 2) don't reset after that and go back to your daily driving, take a look at the average at the end of the week. hopefully hovering around 20. If not, have it checked out.

Thats what I usually get. I get 32 on the highway (speedlimit) and in city I get around 18-22.

If you still have the problem, maybe tell them to reset the pc for you? I had the problem before when I still had my 328. It was all messed up.

[hbiscuit]

how many miles per gallon do you get while idling?

engine is running, car isn't moving...

answer should be painfully obvious.

[marius]

not sure how you guys are getting 24mpg average. I drive a 128i auto and i get 20mpg mostly on highways. I must have a lead foot.

[TagMan]

I noticed recenty that my MPG was low teens after a few traffic jams. Stop and go traffic destroys the gas mileage on the 135i.

[x97Melbourne]

everyone check your tire pressure -- i just checked mine after a "flat tire indicator" i found one tire was at 20 lbs.
rasing this one tire alone to 35 lbs has raised my mileage 15% -- seriously.
check it.

[Bullitt]

Originally Posted by alpnwhite96

how many miles per gallon do you get while idling?

engine is running, car isn't moving...

answer should be painfully obvious.

LOL. Now that you put it that way. What a tragedy for me to overlook that.

[Bullitt]

Originally Posted by x97Melbourne

everyone check your tire pressure -- i just checked mine after a "flat tire indicator" i found one tire was at 20 lbs.
rasing this one tire alone to 35 lbs has raised my mileage 15% -- seriously.
check it.

Good call, I'll check that ASAP.