535i fuel consumption

[ngruzevs@optusnet.com.au]

I have a 1989 535i which I have owned for three months, it has done 197000Kms.

After the first three months of city driving the car has averaged 20L/100 (11.75mpg), this figure is not from the OBC. The OBC CONS1 display shows 99.9L/100 and the Ave speed indicates 299Km. I don't know what's going on with the OBC.

The range display seems to be more accurate until I get down to 1/4 of a tank, a few times the range has gone from 100K to 40K in a matter of 5min. Then I turn the ignition key off and turn it on, then the range reports over 100K.

Ignoring the OBC issues, what type of fuel consumption should I be getting (City driving)? I'm fairly gentle on the accelerator most times.

[Dave M]

I don't have a 535, but will speculate that you probably aren't far from the norm if its serious stop and go driving. If its mixed city/HW, then you might have an issue. Since your OBC has issues, try taking it out for a calculated run on the HW with a full tank. Stick to the speed limit and fill up when you get back. Do the math to see what your pure HW mileage is like. Other than the mileage, how does it run. Hows the idle? Hows the power throughout the rpm range? Does it 'miss'?

Maintenance questions:

Plug condition?
O2 sensor changed in the last, I dunno, 40-50k?
Vacuum leaks?

As for the gas gauge and OBC range featue, I believe its somewhat common. My gauge dives fast between 2/3 and 1/3, then sits forever.

Someone with a 535 will be along soon. I'm just up early killin time

Dave

[ngruzevs@optusnet.com.au]

Thanks Dave, you raise some good points.

The 535i idles roughly compared to my 2.5 Subaru. I'm not sure if it's normal, I don't have another 535i to compare with.

The last owner took it to a BMW specialist just before I bought the vehicle, the report stated that -

1.The engine mounts were harsh
2.Fuel Injectors were noisy

I'll take the car for a run tomorrow and then do the math

[kick7ca]

I have a 1989 535i which I have owned for three months, it has done 197000Kms.

After the first three months of city driving the car has averaged 20L/100 (11.75mpg), this figure is not from the OBC. The OBC CONS1 display shows 99.9L/100 and the Ave speed indicates 299Km. I don't know what's going on with the OBC.

The range display seems to be more accurate until I get down to 1/4 of a tank, a few times the range has gone from 100K to 40K in a matter of 5min. Then I turn the ignition key off and turn it on, then the range reports over 100K.

Ignoring the OBC issues, what type of fuel consumption should I be getting (City driving)? I'm fairly gentle on the accelerator most times.

I have a 535im and do 100% city stop and go driving. All maintainence is up to date and I've changed the oxygen sensor. If I try really hard I can manage 16-17 mpg, but my longer historical average is like 12mpg, from stomping the gas too much I guess, and sitting at stop lights.
What I will say is that the OBC may not be that accurate, I still seem to get 2 weeks out of a tank and overall I'd say the car my car is reasonable on gas for the tank that it is.

[Qube]

20L/100 is insane. When I drive "spiritedly" through a full tank (70+L!!) I get about 14L/100. Definitely need to get it checked out.

NB: avg usually is about 12L/100.

[dennyg]

I get about twenty two mpg highway and 15 in city with a heavy foot. I was getting 27 highway but I changed differential to 4.27 from the 3.91.....I like the added power in town but am paying a premium for doing it. Does anyone own a 535 that doesn't idle rough?

[JerseySi]

95% of my driving is in town, stop/start - the other 5% is out of town/at night, where I cna cruise a little more around 50mph..
My average is always between 13 & 14mpg.. It will rise to around 16-17mpg when i'm out of town, but drop once I get back into traffic..
(1988 535i auto for reference)

Your 11.7 mpg sounds a little on the thirsty side, but then I've seen that sort of figure too... try changing fuel brands - I found it helped for me oddly enough!

Hope this helps!

[Steve's5]

Morning,

Like youself we bought a 535I a few months ago.

A recent trip of 1728k's (Mildura to Canberra and return) gave us approx 10.5 L/100km- stuck to 110k speed limit (wife and child on board) The car has done very few K's <28k and ran really well. Hot days aircon most of the time.

Can't give city figures as we don't live in one.

Engine idles well but hunts a little when cold for 15-30 seconds

Very happy with car and look forward to next trip.

[e34m30SF]

One thing you could try is the air filter. I changed that and my hwy mileage went from 16.7 to about 19. Not great, but when my car was built, EPA had it at 15/19, so as long as i'm in between those two, i'm content.

My O2 sensor is the next thing to change.

And I've grown accustomed to a lumpy idle in 535i's. Weren't these engines designed in the early 80s or late 70s, without all of the electronic sensors and stuff?

[Jon K]

Put (6) 42# fuel injectors in place of stock 17# fuel injectors, then we'll talk about fuel consumption.