Yesterday on the way home I decided to drive like a grandma down the interstate to see what kind of gas milage I could get. I set the cruise to 73mph, reset my consumption counter on my obc and sat in the right lane. The entire trip I sat right at about ~2100rpm and my OBC read 26.7 MPG at the end of the trip.

Car:
540iA
Dinan S1 SW
Intake silencer delete
Resonator replaced with 3" pipe.
Castrol Syntec oil and always run on 93 octane.

Is this unusual gas mileage or does something sound fishy? I decided to try this because I recently did some work and cleaning on my car as well as some modifications and wanted to see if it had affected my gas mileage.

A V8 can cruise very nicely. What were you at like 2k rpms? My e36 used to get 28mpg and that was normal to me.

Yesterday on the way home I decided to drive like a grandma down the interstate to see what kind of gas milage I could get. I set the cruise to 73mph, reset my consumption counter on my obc and sat in the right lane. The entire trip I sat right at about ~2100rpm and my OBC read 26.7 MPG at the end of the trip.



I find it hard to believe. When I use my trip computer, my car has gotten almost 30 mpg on a trip. But when I fill up and calculate the miles versus the gallons it drops substantially to about 24-25. And I have a 2.8

I have a friend with a 540 (with a Dinan chip) and he can't get 15 mpg. I suppose you can get 26 mpg if you cruise the whole time, but include any city driving and it will drop considerably. What do you normally average on that car??

Matthew

I find it hard to believe. When I use my trip computer, my car has gotten almost 30 mpg on a trip. But when I fill up and calculate the miles versus the gallons it drops substantially to about 24-25. And I have a 2.8

I have a friend with a 540 (with a Dinan chip) and he can't get 15 mpg. I suppose you can get 26 mpg if you cruise the whole time, but include any city driving and it will drop considerably. What do you normally average on that car??

Matthew

Once he hits traffic lights and city congestion his gas mileage goes in the toilet.:(

I find it hard to believe. When I use my trip computer, my car has gotten almost 30 mpg on a trip. But when I fill up and calculate the miles versus the gallons it drops substantially to about 24-25. And I have a 2.8

I have a friend with a 540 (with a Dinan chip) and he can't get 15 mpg. I suppose you can get 26 mpg if you cruise the whole time, but include any city driving and it will drop considerably. What do you normally average on that car??

Matthew

Yeah I was cruising the whole time with the cruise control set right around 73mph. I drove for a little over 20 minutes and at the end of the drive it read 26.7. The whole time it was shifting between readings up and down but ended up averaging at that. My long term average is 20mpg but like I said I have done some modifications recently and done some cleaning.

I drove from atlanta to hilton head island last summer & tried the same thing, I got 26.7mpg with the cruise set at 84mph (2000 540i/6 dinan stage 1) but mpg dropped to around 24mpg on the way back due to traffic...grandma-in-the-left-lane causing you to slow down then speed back up again eats more gas then you think...from my expirience with v-8's 'smoothness' is the biggest gas saver because once those fuel injectors open up you can kiss your mpg goodby, but it's well worth it from time to time

edit: I avg 19.7 city/hwy with the normal atlanta gridlock
<grin></grin>

Yeah I was cruising the whole time with the cruise control set right around 73mph. I drove for a little over 20 minutes and at the end of the drive it read 26.7. The whole time it was shifting between readings up and down but ended up averaging at that. My long term average is 20mpg but like I said I have done some modifications recently and done some cleaning.

My 530i has the full compliment of Dinan modifications and it only averages city/highway (albiet LA) 20 mpg. My engine is maintained, tuned and the tires are properly inflated. So unless your are driving on 4 cylinders there is no way your mileage matches mine. The only possible way is if you only drive on the highway and never see a stop light which I would find very hard to believe.:confused

I have seen 26-27 mpg on the highway as well, actually, everytime I cruise between 70-80 mph I'm averaging 26-27 mpg. It's great cruising at 80 mph in 6th gear, turning 2500 rpm and getting 26 mpg.

The main difference between the mpg of my 540i vs my old 328is is that once you hit the gas pedal, the V8 REALLY sucks the gas down. I'm averaging 15.7 mpg in the city (with TONS of hills) driving very conservatively right now.

Of course, when I decide I have to go full throttle everywhere, I'm back down to 12-13 mpg.

hmmm, you might be running a little lean for some reason or other (o2 sensor?)

hmmm, you might be running a little lean for some reason or other (o2 sensor?)

not throwing any codes?

My 530i has the full compliment of Dinan modifications and it only averages city/highway (albiet LA) 20 mpg. My engine is maintained, tuned and the tires are properly inflated. So unless your are driving on 4 cylinders there is no way your mileage matches mine. The only possible way is if you only drive on the highway and never see a stop light which I would find very hard to believe.:confused

Sez you. I have had 2 540s, a 1994 which I still own and a 99 540i/6. I averaged right around 21mpg city with the E39 and I can't seem to push the E34 much above 20 city. This is not what the OBC said, but rather what I calculated from the gas consumed.

It is very easy to drop the mpg of a 540 to 13-ish levels. It is all a matter of driving and traffic.

I average about 16 mpg in my 99 540/6, but I am also in a lot of stop and go traffic and city driving...when I'm crusing on the freeway I watch my mpg gauge and I actually get pretty good mileage when I'm crusing...I went up to my uncle's house up north, and on my way back down crusing on the 101 I averaged in the mid 20's IIRC.

My 530i has the full compliment of Dinan modifications and it only averages city/highway (albiet LA) 20 mpg. My engine is maintained, tuned and the tires are properly inflated. So unless your are driving on 4 cylinders there is no way your mileage matches mine. The only possible way is if you only drive on the highway and never see a stop light which I would find very hard to believe.:confused

If you read what I said, I stated that I reset it for the drive down the highway. Only about 2 miles of this entire drive were done in the city.

If you read what I said, I stated that I reset it for the drive down the highway. Only about 2 miles of this entire drive were done in the city.

Are you basing your observed MPG on the trip computer or actual gallons used (after refilling)? I have found that the trip computer in my E39 is overly generous in MPG by at least 2-3 miles. Kinda like the speedometers in those cars :)

Matthew

Yeah I was cruising the whole time with the cruise control set right around 73mph. I drove for a little over 20 minutes and at the end of the drive it read 26.7. The whole time it was shifting between readings up and down but ended up averaging at that. My long term average is 20mpg but like I said I have done some modifications recently and done some cleaning.
20 minutes is not long enough to get an accurate reading. You are measuring too short a period of time/distance for it to matter, try driving 2 full tanks of gas on the freeway at 73 mph then average your mpg for both, at this point you will have some meaningful data to analyze.

I don't know how the weather is where you live, but since it's gotten warmer here my gas mileage has gone up 1 or 2 mpg.

Are you basing your observed MPG on the trip computer or actual gallons used (after refilling)? I have found that the trip computer in my E39 is overly generous in MPG by at least 2-3 miles. Kinda like the speedometers in those cars :)

Matthew

My trip computer reads consistantly 1.2-1.8 mpg higher than the actual calculated mpg. (miles/gallons)

According to the OBC I've been getting about 19mpg combined driving with about 23+/-mpg hwy. I rarely fill my tank up completely so I havn't varified if the OBC is accurate or not.

have you guys ever left your car one away from turned on with the obc set to range while you fill up your tank. pretty funny.

does anyone have how many gallons of gas an e34 tank holds, from the owners manual? I think its somewhere around 19 but i dont know.

I think it sounds fine..For that road trip, that is what you averaged. The best MPG I have received was 28.6 on the highway in my 528i-5. Cruise Control for 100 miles or so. However, I average 21 as daily driver.

Your car cruised at low rpms for that one trip. It is not a big deal. Drive it around the city for another 73 miles and see what your average MPG turns out to be. I do not know what all teh fuss is about.

Rob