BMW E34 535i fuel efficiency??? - BMW Forum

aliasneo · 10-25-2010, 07:35 PM

Hi guys,

Recently brought a 1992 BMW E34 535i. Absolutely love everything about the car except at the moment the fuel efficiency is through the roof. It's averaging around 21.0L /100kms which is just disgraceful. That's taking it easy by the way. Was wondering what anyone's opinions on this might be, I was thinking it might be the Oxygen sensor, because apart from that the car runs pretty smooth but not too sure.

What sort of average should I be getting??

Thanks in advance

witeshark · 10-25-2010, 08:17 PM

You're right, that's not good economy, about 11 mpg. It should be more like 16 in mixed driving. Up to 22 in good highway conditions.

aliasneo · 10-25-2010, 08:42 PM

Yeah, really not sure what it might be, just wondering if anyone else has encountered the same issues.

Torque · 10-25-2010, 11:09 PM

They're not great on gas no matter what you do ... as shark said, you'll still struggle to get in the 20s ... I've had multiples, they were all like that. As for your 21 liters ... try doing a simple tuneup (you know, the regular: plugs, filters, oxygen sensor) and see where that gets you.

btw, you getting the number from the OBC or are you actually calculating it yourself?

tour96se · 10-28-2010, 02:52 PM

get a 525 if you want good mileage! my little trip computer says i'm getting 28.6mpg on the highway. i would try o2 sensors,plugs,wires,fuel filter,pump,intake boot,air filter..basically a good tuneup. how's the timing? tire pressure? any of the calipars hanging?

aliasneo · 10-28-2010, 06:27 PM

Hey guys, yes these figures are coming from the OBC dash. I'm now getting between 16 & 18 litres/100km's which makes me believe it just has to be the oxygen sensor. Tested out my wires & replaced the spark plugs but yeah It's definitely the O2 I believe. All the timing is going perfectly fine, just basically the fuel is running way too rich.

I love the 525's but got the 535 so I'll stick with it. Still absolutely loving BMW's apart from this, it's my first Beemer and apart from the fuel efficiency It's just an awesome cruiser.

Anyone know where I can get an O2 sensor for a reasonable price, down here in Australia for the Bosch equivalent for my model, I was quoted at $180 AUD so wondering if there is a place where I can purchase one cheaper if anyone knows???

aliasneo · 10-28-2010, 08:42 PM

Ok, I just went ahead and purchased the bosch o2 oxygen sensor. The cheapest I could find it for myself delivered was $107 AUD which isn't too bad I didn't think

Will install when I get it and see if there are any noticeable differences.

witeshark · 10-28-2010, 08:55 PM

Best of luck then!

gidgaf · 10-31-2010, 09:15 PM

AFAIK the biggest factor is that thing on the end of your right leg. My wife consistently gets over 10% better mpg than I do. If you're braking a lot, you're gassing a lot. Plus it's city driving- we were bothered by our 16 mpg also, until the OBC told us our average speed never went over 23.5 mph. Half the drive time is stopped at the light; the other half is going up to 45, cruise at 45, then stopping.
You can always check out the hypermilers for techniques. some of those guys are pretty serious.

1LOBOSS · 11-06-2010, 04:32 PM

Damn and I thought my Ram Hemi 4x4 was bad at 15-16L/100k in the city and it's a 5.7L@390hp-407Tq. Good luck with the fix

aliasneo · 11-10-2010, 10:28 PM

Okay guy's got the part in today, finally, USPS took their time. I got the Bosh premium oxygen sensor & all up including delivery I paid $107 AUD which isn't bad considering they are going for $180 AUD at trade price. Really starting to love this car even more each and every single day. Will install the o2 sensor tomorrow when my car's cooled down etc & will keep you all posted.

Another thing about me being a little heavy on the pedal, my girlfriend drove my car and got it down to 19L/100km so I'm sure I've contributed slightly haha!

Cheers guys

grey5351 · 08-30-2011, 07:46 AM

Man I could be posting the exact same posts as you right now eg just bought my first beemmer , 89 535i manual, lovin it more each day & the most concerning right now the fuel consumption. I'm getting bout 18-19liters/100km whilst trying to drive conservatively. I've changed the oil/filter air filter fuel filter spark plugs dizzy cap & rotor & was now thinking o2 sensor. How did you go with the replacement of your o2 ? Did it improve fuel economy at all ?

aliasneo · 08-30-2011, 08:09 AM

Hey mate I ordered the o2 sensor from ebay, it was a bosch

It was a little challenging but eventually got in there and got it loose. I actually no longer have the BMW, my girlfriend hit me from behind and even though the boot was slightly pushed in, the insurance company classified it as a ride of and I brought a Toyota Soarer (Lexus SC 300) instead. It's pushing out 260rwks and if I give it a boot full still uses less fuel than the Bimmer does about 17L to 100KMs and if I drive it normally only ever overtaking now and then I get 13L to 100KMS. A part of me misses this car for comfort and the massive sun roof but with fuel prices and the fact that I have a faster car with similar features to the BMW I'm glad my girlfriend hit me.

grey5351 · 08-31-2011, 06:19 AM

Well first of all sucks arse about the stack with the misses but nice choice on the replacement. Boost is fun & very addictive & local performance parts availability is awesome. Did you ever get to fit the o2 sensor before the prang & if so did you notice any difference in fuel economy ? just asking as my symptoms or lack of sound similar to yours , my car drives fine doesn't hesitate when accelerating & doesnt blow any smoke. My car is returning bout the 20 l per 100km , I just can't fathom this 3.5l 6 would chew 20l /100km being driven just as you described. going to do a diagnostics check with a scope on the weekend but was just curious how you went .

aliasneo · 08-31-2011, 10:15 AM

Yeah I did fit it and had it working a couple of months before the prang! I did notice the difference slightly but overall it still drinks and I came to accept that for a 1992 535i it was normal to expect higher than usual fuel usage when I took into consideration it's age and the fact that it was made during a time when Petrol prices were nothing to really worry about. I would assume that the higher than average fuel mileage came from a combination of more than just the o2 sensor but it was a good starting point and if I still had her which at times I wish (not really haha but I had a soft spot) I would just slowly go through the list. Amazing cars for cruising, loved every moment of it!