Erratic MPG

My mileage seems to vary by a great deal depending on the driving conditions--seemingly much more than my old E39. My E39 averaged about 21 MPG over each tank of gas and for very short periods it would go as low as say 18 mpg in heavy stop and go traffic and up to perhaps 26 mpg on the open freeway. The mileage was very consistent from fill up to fill up.

With the F10, for a full tank of gas (about 13-16 days of driving) my mileage can range from about 20 mpg to about 26 mpg depending on whether the freeways have been running at normal speed vs. stop and go traffic. And for short trips around town I can get as low as 14 mpg and on a long freeway road trip I can get up to 33 mpg. I never saw these large swings in my E39.

Has anyone noticed this? Is it normal for the heavier F10?

Originally Posted by DavidZ

My mileage seems to vary by a great deal depending on the driving conditions--seemingly much more than my old E39. My E39 averaged about 21 MPG over each tank of gas and for very short periods it would go as low as say 18 mpg in heavy stop and go traffic and up to perhaps 26 mpg on the open freeway. The mileage was very consistent from fill up to fill up.

With the F10, for a full tank of gas (about 13-16 days of driving) my mileage can range from about 20 mpg to about 26 mpg depending on whether the freeways have been running at normal speed vs. stop and go traffic. And for short trips around town I can get as low as 14 mpg and on a long freeway road trip I can get up to 33 mpg. I never saw these large swings in my E39.

Has anyone noticed this? Is it normal for the heavier F10?

Yup should be normal the 550i makes such large swings because its extremely
sensitive on the gas petal. If I drive surgically, it is possible to get close to 30mpg
but If I pull a little to get into an exit, will go to 19mpg...immediately even if the average was taken over hours...

How often do you reset the computers?
Let the onboard one count forever, you'll get a good picture of combined. If your trip computer is on auto reset, it will be erratic, mine is too. After onboard has 2500-3000 miles, you will have a good picture of your combined to the point where a friend test driving it or a long stretch on cruise don't do much either way.

Originally Posted by bmw_enthusiasm

Yup should be normal the 550i makes such large swings because its extremely
sensitive on the gas petal. If I drive surgically, it is possible to get close to 30mpg
but If I pull a little to get into an exit, will go to 19mpg...immediately even if the average was taken over hours...

Looka like he has 528 right?

Originally Posted by DreamCar

Looka like he has 528 right?

Yup I am surprised with his mileage though...it so similar to the 550's

my 528i is getting 30-31mpg in a mix of highway and suburban driving. Probably 65% highway.

Originally Posted by snj1013

my 528i is getting 30-31mpg in a mix of highway and suburban driving. Probably 65% highway.

that is really nice mileage!

I get 21.5 or so currently. I have 70% highway. I enjoy the car in the city portion of the drive which brings my average down. I took a tank to see how efficient I could drive a 550, I think it was 23.8, lots of coasting. It just wasn't worth the 2mpg.

Originally Posted by cynerjist

that is really nice mileage!

I get 21.5 or so currently. I have 70% highway. I enjoy the car in the city portion of the drive which brings my average down. I took a tank to see how efficient I could drive a 550, I think it was 23.8, lots of coasting. It just wasn't worth the 2mpg.

As per the forum for a 550 i think you are getting pretty good milleage

I reset the trip computer only after each fill up. I do let the onboard computer count forever and it was around 23.5 last time I checked. I got horrible mileage for the first 500 miles and the onboard computer showed something like 19 mpg. I assumed it would get better during the break in period and it did. The current 23.5 average is about 10% better than my old E39 so I'm pleased about that.

SNJ, the only way I can get that kind of mileage is on the open freeway with very little braking. The minute I slow down/speed up or get into stop and go traffic or go through neigbhorhoods with stop signs, etc., the mileage drops significantly. On my last tank of gas I got 22.6 mpg because the freeways have been unusually congested. The tank before that was closer to 26. My mileage is split about 50-50 freeway and city/neighborhood driving. I'm a fairly conservative driver (two tickets in 27 years) so I'm not heavy on the pedal--hence the 528.

Originally Posted by DavidZ

I reset the trip computer only after each fill up. I do let the onboard computer count forever and it was around 23.5 last time I checked. I got horrible mileage for the first 500 miles and the onboard computer showed something like 19 mpg. I assumed it would get better during the break in period and it did. The current 23.5 average is about 10% better than my old E39 so I'm pleased about that.

SNJ, the only way I can get that kind of mileage is on the open freeway with very little braking. The minute I slow down/speed up or get into stop and go traffic or go through neigbhorhoods with stop signs, etc., the mileage drops significantly. On my last tank of gas I got 22.6 mpg because the freeways have been unusually congested. The tank before that was closer to 26. My mileage is split about 50-50 freeway and city/neighborhood driving. I'm a fairly conservative driver (two tickets in 27 years) so I'm not heavy on the pedal--hence the 528.

I misread your post. I see what you are saying now. I think the stop and go, speed up slow down, has a noticeable impact on mpg on all the 5's. 50/50 freeway/city is probably the most sensitive combo to see your mpg drop in congestion, stop-go, etc (eg. 80% highway is harder to bring down overall mpg and 80% city is going to be low mpg already)