E39 528i burning cash - 20.2L/100kms!

[jeffbebe 1559]

Something's not right. Averaging 20.2L of petrol per 100kms at the moment. Insane. Going to dispense with the aftermarket cold air intake it had when I bought it, which should help but I don't think that can be the sole cause.

Any likely culprits? Lambda sensor? Vanos seals? And anyway I can pinpoint the problem without a mechanic's help?

[my_e36 43]

You sure have a heavy foot or stuck in traffic a lot. Check your tyre pressure, air filter and engine oil condition for starters. Is your engine running smoothly? Smokes? I doubt a CAI helps much, but using 95 instead of 91 will help a bit from my experience (you gain fuel milage more than offsetting its higher price).

Get a computer scan from a reputable workshop, for around half hours labour or so. The results and the mechanics opinions will be invaluable comparing to you spending money on parts trying to solve it blindly.

Glenn @ Botany Motor Works is our forum sponsor, very helpful and know his stuff

also BM Workshop does good jobs on BMW too.

[jeffbebe 1559]

It's 90% city driving for sure and I'm not particularly heavy footed - the opposite if anything - and I already use 95 not 91 so my feeling is there is a mechanical issue.

It's been scanned recently and nothing unusual showed up, had a full service (all filters replaced, oil change, etc) and the engine runs perfectly otherwise (idles around 500-600rpm), no smoke or anything untoward.

Incidentally, anyone know how to reset the L/kms counter on the MID. I can't find the manual for my version of the MID (only later ones). It's a 9/96 E39 528i.

Edited June 3, 2012 by jeffbebe

[NZ BMW 368]

This is similar to what I get in rush hour commuting in Auckland, is this not normal? I get good milage on the open road Auckland to Whangarei on less than a 1\4 of a tank.

[BM WORLD 1283]

could be very dirty pod filter , or oil and dirt has passed through it and dirtied the maf sensor??

have had that happening before.

cam sensor faulty ??

vanos soliniod faulty??

bring it around can have a look and try a few things if you like.

cheers brent

even my thristy az 544i got 12L/100km yesterday driving to the mount.

or 14 to 15l around town etc

only does 20L when pulling a car transport trailer .

[jeffbebe 1559]

could be very dirty pod filter , or oil and dirt has passed through it and dirtied the maf sensor??

have had that happening before.

cam sensor faulty ??

vanos soliniod faulty??

bring it around can have a look and try a few things if you like.

cheers brent

even my thristy az 544i got 12L/100km yesterday driving to the mount.

or 14 to 15l around town etc

only does 20L when pulling a car transport trailer .

Thanks Brent. Might try and pop over later today if you're around. I'll drop you a line.

[tonylauno1 7]

It might be aftermarket wheels which are heavy...

I have found using 5w30 engine oil instead of 10w30 and new differential oil also helps. This saved me about 2l/100km

driving around Auckland in stop start traffic 90% of the time I do get 14-15L/100km in my 328ci but it does get down to 8l/100km on long trips. Probably quick traffic getaway doesn't help.

[charles28 136]

My 96 528i averaged 14.1L/100k using 95 fuel.

about 50% of the driving was back roads (still 50km areas) without much stop and go.

I remember one day I was stuck in lots of traffic and it went up to 17L/100k.

My current 1989 325i is averaging 11.9L/100k with the same driving conditions, which to me is odd, since its a much older design technology wise.

[Docile 64]

could be dirty plugs..

when did you last service your car?

[kiwi535 538]

when i got my 535 from the previous owner in Auckland (he lived and worked right tin Central city Aucklnad so did virtually cold run stop start.The guzzle o meter said average was 17 l 100k.In the time i had it the round town verage was 12-13 but it was not much idle - stop- start.On a trip i could get it down to low tens if i really tried say Wlg Tauraunga(staying at goooood speeds though)

[Docile 64]

probably built up carbon on the pistons if it lived its life start up stop

[sp8s 1]

Release the handbrake

well no-one else said it.......

[isis 16]

I now feel better as the x5 averages just under 15l around town

[1rotty 40]

I just did a pretty heavy footed return trip from Hastings to Gisborne which is all windy roads & hills & got 13/100 in the 540.

Not helpful in the slightest but hey..it made me feel better

[jeffbebe 1559]

I just did a pretty heavy footed return trip from Hastings to Gisborne which is all windy roads & hills & got 13/100 in the 540.

Not helpful in the slightest but hey..it made me feel better

haha!

[jeffbebe 1559]

Spent a couple of hours checking filters, cleaning everything I knew how to clean and testing the car. I worked out how to reset the L/kms counter on the MID so went for some round town driving then a longer motorway drive.

What I discovered is that my own round town driving (after about 20kms - so not hugely accurate) is using around 17L/100kms but on the longer drive (again not that accurate but over around 80kms) I used less than 9L/kms. So the previous average must have been from the Ks clocked up by the previous owner (I admit, I probably should have checked that when I bought the car). So at least my own fuel consumption is not as bad as I originally thought, but 17L/100kms still seems pretty high.

Since then I found this: http://spaghetticoder.org/bmw/wds/zinfo/246010001.htm

Looks like my A5S310Z transmission has an adaptive transmission control that selects one (of 4?) presets based on your driving pattern. I'm guessing that my predecessor liked the car pretty sporty. I've never really paid much attention to the L/kms gauge before but I watched it like a hawk today. I noticed that my car doesn't kick up gears very quickly when you accelerate gently, preferring harder acceleration which is not my normal driving pattern, which means my regular driving is using quite a lot of fuel as the car is sitting in low gears at higher revs a lot of the time when I drive round town - which is most of my driving.

I realised that by altering the way I drive to suit the auto gear changes I could conserve some fuel but the transmission preset seems to suit a sporty, uneconomical ride. If I'm right and it's the adaptive transmission control preset that doesn't suit me, does anyone know how to reset it?

Edit: So apparently you can reset with a scan tool... Can anyone help?

I should add that I also tested the car around town manually changing gear with the Steptronic controls and the fuel consumption was reduced to around 15L/100kms over a similar distance. I realise that over such short distances the measures are pretty inaccurate but I watching the gauge as I drove it was pretty clear that changing gear to suit my own driving was using a lot less fuel.

Edited June 4, 2012 by jeffbebe

[1rotty 40]

The adaptive trans will adjust itself to ur driving style over time so resetting only shortens the inevitable

[nath 134]

That transmission feature is a pain. An S4 audi I had was like that, and was always sluggish when I felt like a sudden blast at the traffic lights.

If you are getting fuel economy like that; aside from terrible around town driving skills, there's something wrong with the fuel mixture controls. It won't be carbon build up, wheel weight, wrong fuel or any such trivial things. It will be something that has a more direct relation to fuel than that.

Bad airflow meter, seriously bad injectors or other mucky old sensors whichever ones it has.

[Allanw 1071]

The actual revs of an engine have very little to do with it's fuel consumption - it's the load and efficiency of the engine at a given RPM that determine it's economy. Within a certain RPM range, the engine will use the same amount of fuel regardless of RPM, as long as the required power is the same (i.e. an engine producing 60hp at 2000 RPM may use the same amount of fuel as the same engine doing 3500 RPM but still only producing 60hp, but more or less RPM may actually increase consumption). An example is the Subaru engine I have in my VW transporter - the fuel usage is within about 5% from about 2000 to 4200 RPM at the same load, and outside of that range it increases.

The time spent accelerating is when fuel is used the most.

Do you have a high OBC? (with the text display?) You can use it to tell you the coolant temp - maybe the thermostat is stuck part open? It'll run richer when it thinks it's cold.

I know our engines are different, plus I have manual trans, but we get about 10.2L/100kms "commuting" (no heavy traffic here, half is winding, hilly open road, 100k limits, but 35 and 55 corners etc) - although when the Mrs was away, I used only 9.5L/100kms doing the same commute. We have the climate air going all the time too.

Just did a trip Whangarei to Tapeka (near Russell) with 3 adults, a child and the boot absolutely CRAMMED full, and two bags squeezed in the back seat, and got 8.0L/100kms on the way up, and after the return trip, was on 8.4L/100kms. Another time, just me in the car, Whangarei to Warkworth I got 7.0L/100kms sitting on 100, but just cruising along. That's on the OBC, but it's always within 0.1L/100 kms of what Fuelly.com shows based on my fillups.

I think given the differences between the two cars, your open road figure is probably close to correct. The commute seems a bit hungry though! I have a friend who lives in glenfeild, and drives to silverdale each day (pretty good trafic wise), and local groceries etc driving on weekends (with a HEAVY foot!) in a 540i touring and gets about 14-15L/100kms. On a trip, he got it down to about 9. He seriously has a heavy foot though! Full throttle up to the speed limit (ish) usually, and was only getting about 15K from his tyres (dunlop sport max or something). I'd have thought that even with a typical Auckland commute, that a 528i would be getting 12 to 14 without trying too hard.

Even 17 seems high - better off with a 540i if that's the case!

[jeffbebe 1559]

That transmission feature is a pain. An S4 audi I had was like that, and was always sluggish when I felt like a sudden blast at the traffic lights.

If you are getting fuel economy like that; aside from terrible around town driving skills, there's something wrong with the fuel mixture controls. It won't be carbon build up, wheel weight, wrong fuel or any such trivial things. It will be something that has a more direct relation to fuel than that.

Bad airflow meter, seriously bad injectors or other mucky old sensors whichever ones it has.

Thanks.I agree that it must be something affecting fuel mix control but no idea what yet, though Brent's hopefully going to help pinpoint the issue.

Fuel consumption is obviously at its worst while accelerating, cruising no problems - in fact fuel consumption is very good - is there an explanation why the fuel mix on acceleration would be hungry but okay when cruising? And I definitely don't have a heavy foot, quite the opposite actually, have been trying lately to ease off even more to see if it affects the fuel consumption but hasn't made much difference.

[jeffbebe 1559]

The adaptive trans will adjust itself to ur driving style over time so resetting only shortens the inevitable

I've had the car for almost 2 months though I probably only drive it 10-20mins max per day. Any idea how long it takes to adjust? Wondering if the short trips I mostly do mean that the ATC doesn't read it as a change in driver pattern but as a one off anomaly and not adjust the preset. Anyone know much about these things?

I know, I know... I should do a manual conversion and save all the bother.

[e38king 1]

Not helpful in the slightest but hey..it made me feel better

I have a similar story as well. We just went down to Taupo and back in the family Airtrek. I thought I would alter my driving style slightly to see if I could get better fuel mileage. Instead of putting my foot down and the car changing down gears to get up a hills at a constant speed, I kept my foot steady on the accelerator and let the car naturally find its own speed. End Result - 70 more kms out of a 50l tank of gas!

Slightly helpful but prob not: My tank (e38 735i) averages around 14L/100km around town and will easily average under 10 on long trips (9.9L/100km to Gisborne and back, and that was driving it pretty hard through the gorge between Opotiki and Matawhai both ways).

Edited June 5, 2012 by e38king

[jeffbebe 1559]

Do you have a high OBC? (with the text display?) You can use it to tell you the coolant temp - maybe the thermostat is stuck part open? It'll run richer when it thinks it's cold.

How do I know whether it's low or high OBC?

[camera doctor 25]

My 530i used lots of gas when the thermostat was buggered, I guess it was overfueling, plus it seemed to use oil - washing the bore ?

New thermostat fixed both issues.

[Allanw 1071]

How do I know whether it's low or high OBC?

Sorry, I actually meant cluster! Low cluster has a picture of a car, High cluster has a text display and no car picture. You can unlock it and get it to show the coolant temp (I can't remember how now - Google)

Otherwise you can get Glenn or someone to watch the real-time data to see what the operating temperature is via a scanner etc.

The gauges on these things seem to be calibrated to show normal from actual temps of high 70's up to well over 100, so you could be running near the low end a lot, and it's burning more gas than needed. Even though the gauge shows it up to temp, it may be cold.