E39 Petrol Economy problem (?)

[Tristan 338]

Hi guys

I've read a bit about what could cause petrol diseconomy.

The car in question is a 2001 E39 530i. Don't know much about it's history other than what I've changed on it, which isn't much.

Day to day driving, I do about 20-30kms. This is all "around-town driving" Even when the car is driven with the utmost economy in mind, the fuel economy is up at 13-15l/100km ... Obviously with more aggressive driving that increases substantially.

I'm fairly sure that this car can do a lot lower... I think Yongxi mentioned his 330i has done around 8l/100km - Obviously his car's a fair bit lighter but to near double to petrol use I think is a lot.

What can I have looked at that could affect the economy?

I go back to an old thought, I don't remember the car being this thirsty before the exhaust was changed over by Wolf mufflers.. I asked AJ if he thought this could affect it and I seem to remember he said it wouldn't drastically. Then again, I only drove the car on the factory exhaust for a month or two.

Any thoughts are appreciated.

Thanks

Tristan

[NZ BMW 368]

Probably Vanos?

[Tristan 338]

Probably Vanos?

Hi

I'm sorry but what would be wrong with the VANOS to cause the diseconomy?

My knowledge of engines is ... limited ...

[camera doctor 25]

Is the car running at temp ? The thermostat on my 530i was stuffed, car was running cold and used lots of gas.

[BM WORLD 1264]

vacuum leaks , bad maf , vanos not working ,thermostat not working,

bad O2 sensors ,

best to get it scanned first

[Tristan 338]

Is the car running at temp ? The thermostat on my 530i was stuffed, car was running cold and used lots of gas.

Only temp problem that I can see is the external temp. which is at -40degrees c. Dash temp gauge seems to be working fine.

vacuum leaks , bad maf , vanos not working ,thermostat not working,

bad O2 sensors ,

best to get it scanned first

do you do scanning brent? if so i may as well get that done when I pick up that stuff. how much would it cost?

[jeffbebe 1559]

Hey Tristan. I've got an E39 528i and when I first got it I was similarly concerned about fuel consumption. I average around the some mileage as you and nearly all is from cold and very short distances, so the car rarely gets a chance to warm up.

As a result, my fuel economy sits around the 18-20L/100 mark. I've checked everything and the engine is running perfectly - E39's are just hungry when they're cold and if most of your driving is stop start, low gear driving when cold you're going to use a lot of fuel.

If I get on the open road and cruise at a nice constant speed then the fuel economy can be as low as 6-7L/100kms. Sounds to me like yours is running just fine.

Replacing the vanos seal might help - a little - but it's a lot of work without really knowing if it will make any difference at all. A new E39 was expected to do 11-14L/100kms with a balance of open road and urban driving. If you do more round town your consumption will be poorer.

[Tristan 338]

Ok Jeff, that sounds promising (in the sense that I don't have a problem)

I live about 5 minutes from town, my driving consists of 6am very cold starts driving 5 minutes to work. From then on it's only up to uni and back to work a couple of times a day at most.

Short, stop-start driving. The engine is only warm from the sun.

Thanks.

[jeffbebe 1559]

Ok Jeff, that sounds promising (in the sense that I don't have a problem)

I live about 5 minutes from town, my driving consists of 6am very cold starts driving 5 minutes to work. From then on it's only up to uni and back to work a couple of times a day at most.

Short, stop-start driving. The engine is only warm from the sun.

Thanks.

Sounds pretty normal to me then, or actually pretty good considering both your daily driving and the age of the car!

[NZ BMW 368]

I estimate that I would get anywhere from 450-500km a tank max in city driving. That's based on a 15-20 minute commute on suburban streets when I drive to work.

I think that sounds similar to what you're getting I was convinced that my Vanos and O2 sensors need changing but that might just be me being paranoid as on the open road I get excellent mileage.

Edited October 12, 2012 by NZ BMW

[allan 295]

Give it a surprise and drop $80.00 of 98 in it and some open road next floor it look in the rear mirror and watch the developing cloud as you blow all the crap out of the exhaust system then watch the ltrs/ks drop chuckle chuckle . All joking aside give it a decent run and let it warm up properly the 5s are a highway vehicle not a city dweller in the five odd years I had mine it never did less than 30 miles/ gallon, 9.4ltr/100k or 735 to 750k to a tank full.

[Tristan 338]

Give it a surprise and drop $80.00 of 98 in it and some open road next floor it look in the rear mirror and watch the developing cloud as you blow all the crap out of the exhaust system then watch the ltrs/ks drop chuckle chuckle . All joking aside give it a decent run and let it warm up properly the 5s are a highway vehicle not a city dweller in the five odd years I had mine it never did less than 30 miles/ gallon, 9.4ltr/100k or 735 to 750k to a tank full.

I always run it on 95, and give her a drink of 98 a couple of times a month too.

But yeah, might have to give it a good run down to a mate's farm for a weekend.

[NZ BMW 368]

Give it a surprise and drop $80.00 of 98 in it and some open road next floor it look in the rear mirror and watch the developing cloud as you blow all the crap out of the exhaust system then watch the ltrs/ks drop chuckle chuckle . All joking aside give it a decent run and let it warm up properly the 5s are a highway vehicle not a city dweller in the five odd years I had mine it never did less than 30 miles/ gallon, 9.4ltr/100k or 735 to 750k to a tank full.

Is that based on city or open road driving?

When I check my "average speed" in the computer it is about 34km/h, and that includes some open road driving.

[allan 295]

Nathan it is based on about 75% highway and 25% city from memory like I said the 5 series it a highway cruising vehicle not a city dweller.

[Tristan 338]

EEk, my E39 528 averaged 10.1 for the whole 150,000 k we had it for lots of fast driving 20,000 k to a set of tyres.

sounds like you have a serious probles best ever was 7.3 to Rotorua at an average speed of 97kmh

Was it manual?

[tmase 19]

My E39 530i gets similar to you round town (13-14.5 l/100km), seen 7.8 l/100km on a run down to Dunedin. Vanos Seals are on my to-do list when I get home. I'll let you know if this improves things (hope it does!)

[antil33t 90]

My E34 525i Touring gets 16.5L/100KM(OBC). (M50NV)

But if I decide to use it properly, it can get 8L/100km on the Open Road, which it was meant for.

Probably best to get it scanned...