What gas mileage should a '91 535i be getting?

[Kamil]

Ok, my higher mileage 535i 5-speed gets between high 21's to mid 22's on the highway (as per OBC), with somewhat enthusiastic driving.
When stuck in or around the city, that number drops down to 19's... high 18's at worse.

Is this normal mileage?

My plugs, air filter, fuel filer are fresh and I've clean the t-body and AFM (not adjusted tho), and I've also adjusted the valves... the only thing that might have an effect on the gas mileage is an old muffler and/or O2 sensor, possibly primary wires, cap & rotor, tho I doubt the last two would have an effect on gas mileage.

No check engine lights are on, but my idle is a bit off... I'm thinking dirty ICV.

Otherwise, it's runing great. :)
I'm not complaining... just inquiering about other's gas mileage... I see folks w/ 525 post numbers into 30's (!!).

[Bill in MA]

Although I have to calculate the mileage as my OBC reads an overly optimistic 29-30 mpg...I wish!

Bill
92 535i turbo

[Mr Project]

The OBC readout is based on a correction factor you can set yourself. True gas mileage should be determined using your miles driven and your gallons to fill. Then compare that # to your OBC readout and adjust the correction factor until they match.

To adjust OBC:
Press 10 & 1000 buttons simultaineously (maybe it's 1 and 100?)
When "Test" appears, go to test # '20'
Adjust value (1000 is default, mine is best at around 920 with the D'sylva chip)

Now, that being said: I've read stories on here of people pulling 27mpg out of 5-speed 535s! Obviously all highway. I recently have been achieving 25ish on the interstate at about 75 mph, which is pretty high for me, usually I was around 22-23. Warmer weather, no A/C, the D'sylva chip, and not driving too hard seem to help a bit.

In town, I've gotten as low as 15-16 with aggressive driving and stop-and-go, so I think you're right in the ballpark, if the OBC reading is correct.

[Russell]

I can get as high as 31-33 mpg if I drive at 60-65 mph-very hard to do. Most of the time 27-29 mpg at interstate speeds of 70-75. However, if I am in heavy and I mean heavy stop and go, I can get as low as 10-12 mpg. Even then my "usual" in town driving is usually 15-19 mpg. Mix of city(heavy stop/go) and country roads on my daily commute is usually 23-24 mpg. The OBC is usually different than tank measurements. It measures about 1/2 mpg low.

Just my observations.



Ok, my higher mileage 535i 5-speed gets between high 21's to mid 22's on the highway (as per OBC), with somewhat enthusiastic driving.
When stuck in or around the city, that number drops down to 19's... high 18's at worse.

Is this normal mileage?

My plugs, air filter, fuel filer are fresh and I've clean the t-body and AFM (not adjusted tho), and I've also adjusted the valves... the only thing that might have an effect on the gas mileage is an old muffler and/or O2 sensor, possibly primary wires, cap & rotor, tho I doubt the last two would have an effect on gas mileage.

No check engine lights are on, but my idle is a bit off... I'm thinking dirty ICV.

Otherwise, it's runing great. :)
I'm not complaining... just inquiering about other's gas mileage... I see folks w/ 525 post numbers into 30's (!!).

[JonE]

My '90 535iA gets about 17-19mpg city (EAT chipped) and about 22-24 highway. Mr. Project, can you clarify those instructions for the OBC adjust? Mine typically reads about 2mpg low and would like it more accurate. Does the adjustment from 1000 down adjust the mpg readout up or down, is this trial and error?
Thanks in advance.

[winfred]

my all time best in the 535ia with a 3.91 diff is 27.4 by math a couple 1100 mile one way trips to virgina ago, how ever the last trip only bested 22.5 over the same roads at the same speeds

[George M]

would say that is about right...my 90 735iL on a recent road trip got 23.5mpg or so when cruising between 60-70 and 22.5mpg at about 80mph or so.
In town, mileage falls way off....about 17mpg...depending how much foot I use. The E-32 with M-30 would be best served with having an on/off switch instead of a gas pedal. If I have to explain that...you aren't a real car guy :-)
Hey Bill...how bout a brief review of your 92 535i turbo?...set up?..boost...any pics?
George

[TimGinCentralNJ]

...although I've not yet done the plugs/cap/rotor, etc and run approx 35 psi all-around.

Tim G.


Ok, my higher mileage 535i 5-speed gets between high 21's to mid 22's on the highway (as per OBC), with somewhat enthusiastic driving.
When stuck in or around the city, that number drops down to 19's... high 18's at worse.

Is this normal mileage?

My plugs, air filter, fuel filer are fresh and I've clean the t-body and AFM (not adjusted tho), and I've also adjusted the valves... the only thing that might have an effect on the gas mileage is an old muffler and/or O2 sensor, possibly primary wires, cap & rotor, tho I doubt the last two would have an effect on gas mileage.

No check engine lights are on, but my idle is a bit off... I'm thinking dirty ICV.

Otherwise, it's runing great. :)
I'm not complaining... just inquiering about other's gas mileage... I see folks w/ 525 post numbers into 30's (!!).

[Mr Project]

The OBC adjustment is probably a trial-and-error at best. Here are my notes, though:

Lower correction factor makes the OBC read higher.

Wait until you fill up, calc your 'real' mileage, then make your adjustment. The change is immediate, so keep adjusting and exiting until the OBC readout matches your 'real' calc. Probably have to do this for a few tanks to get things really 'in sync'.

[Mr Project]

Oh, and every once in a while mine resets to 1000. Not sure why... it's not related to a battery disconnect, and I don't have any other clock/mileage/radio resetting issues.

[bahnstormer]

my 91 535im pure highway trip - max 22mpg (i have 235 255 tires)
my 90 535ia pure highway trip - max 21mpg (oem 16's)

city w/ the 535im i get maybe 12?
city w/ the 535ia i get usally 9

city means stop and go no more than 40mph for me...
how on earth u got 19 in the city i will never know....

[Warren N.CA]

1989 Model, EPA rating is as follows: 15 City / 23 Highway.



Ok, my higher mileage 535i 5-speed gets between high 21's to mid 22's on the highway (as per OBC), with somewhat enthusiastic driving.
When stuck in or around the city, that number drops down to 19's... high 18's at worse.

Is this normal mileage?

My plugs, air filter, fuel filer are fresh and I've clean the t-body and AFM (not adjusted tho), and I've also adjusted the valves... the only thing that might have an effect on the gas mileage is an old muffler and/or O2 sensor, possibly primary wires, cap & rotor, tho I doubt the last two would have an effect on gas mileage.

No check engine lights are on, but my idle is a bit off... I'm thinking dirty ICV.

Otherwise, it's runing great. :)
I'm not complaining... just inquiering about other's gas mileage... I see folks w/ 525 post numbers into 30's (!!).

[DanH]

Here is a nice write up on how to set hidden OBC functions and it also included a formula for calculating the Correction factor for fuel mileage.

http://home.iae.nl/users/bts/obc.htm

Here is a note and formula for setting Function 20:

The average fuel consumption value can be calibrated from the OBC. Function 20 is used for this.
Fill the fuel tank to the maximum. Reset the day trip counter. Run the fuel tank nearly empty and fill the fuel tank again to the maximum. This will give you the fuel consumption.

New Correction Value = Old Correction Value * OBC Fuel consumption (in MPG or l/100Km) / Actual Fuel Consumption (in MPG or l/100Km)

[DanH]

Supposedly you can set a speedometer correction factor too, with function 10.

Has anyone got this to work?

My speedometer reads about 5 mph high at 80mph.