help with consumption please

[Geoffro1]

Please help with ideas where to start with the heavy fuel consumption, 525i auto. I know it will never be "light" on fuel but sitting at 13.5L/100km mixed driving(town and some freeway)
According to research they should get about 8L/100km open road, I tested other day on a 40 km run on freeway @ miss daisy 100km/h and was sitting on ave 9.9L(not right I am sure). I must still do plugs but service/filters etc all up to date. Now to figure out this whole O2 sensor/cat setup. Apparently cats get clogged some time after 160k (I'm on 146k) also 525i for SA only had cats in downpipe do not so quick to just toss and fit straight pipes Ideas on culprit pls, I know we cannot fix it over the net!haha but seems plenty knowledge and experience at hand here(OH and I drive like miss daisy at moment, after all the car is only 100kg heavier than an E90)

 

[RAArmstrong]

Its definitely going to need a fuel filter as I can almost guarantee that it will have never been changed and that will probably make some difference...

I don't know all that much about the M54 engine though so will let the more experienced guys chime in

 

[Budleigh]

Give it a good service, change all the filters and oil, and see where you are after that.

 

[Remerus]

Purely personal experience but try running a bottle of injector cleaner through the tank...

It's around R40-R50 for a bottle and on my own cars it made a useful difference.

My 528i went from 13.2l/100 to 11.4l/100 after a bottle and the ex-730i (RIP) went from 16.7l/100 to around 15l/100 (but that took a few bottles because she'd been standing so long.)

 

[Blue Shirt]

Assuming all normal service items such as spark plugs, air/fuel filters ets are up-to-date, you should consider changing the VANOS seals. They collapse on most M54 engines and will cause loss of torques at low rpm and heavy fuel consumption.

 

[Charlie Brown]

yip, i'd changed all the filters with good quality ones, then the vanos and re-test.

Will be improved i'll guarantee you, but not quiet 8l/ 100kms.

 

[Geoffro1]

Thanks for the advice guys! I will do the suggested. I'm not expecting polo consumption but the 7km/l in town is KILLING me!! Its not even stop/start all the time with much of it @ 60kph(combined robots and bit of freeway here and there). My E30 323i (many years ago) spent most of its life "filling the revcounter" robot to robot, was way less than my current consumption...

 

[markbunting71]

Do you have triptronic maybe you should try changing gears yourself around town? Just a thought


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[Livewire]

I have a 2002 525iT, +-178 000km

Getting 8.5km/l (11.8 l/100km) and i have done 5000km so far.

 

[Hybrid O']

Sounds too high

My N55 with Like i Stole it sometimes, gives me 10l / 100km with in town driving.

 

[AdiS]

Have you had diagnostics run to check if anything like maf sensor could be faulty? Also, vanos seals will help as well. But the fuel consumption at your stated rates IS too high.

Start with all the basics that others have mentioned.

 

[Geoffro1]

Thanks guys, I have put new spark plugs in (@R80/plug) and voila! I am down to 12,2L/100 km(from 13.5) not huge difference but better. In fact on a open road trip the weekend she averaged 7.3L/100km @ +-110kph, quite impressed with that!

 

[sash]

thats good news, but i would still do the check up on your sensors, fuel filter, air filter. check for leaks on pipes any sign of damage.

There are owner on hear that have done this kind of maintenance and are getting amazing consumption.

 

[obbzie]

your revised consumption of 12.2l/100km is more or less par for the course - thats an auto for you.

Enjoy the car now - you will never get the consumption lower than this in town - assuming you have now serviced it and mechanically its in order. Open road, if you can get it to low 9's thats good.

BMW's quoted consumption figures are never achieveable in real life situations, i.e. day2day.

Just be thankfull you dont own a merc - they are the worst when quoting consumption figures.

 

[M-thusiast]

I have a 525iA around same mileage in msport guise, and I currently average around 10.5L/100km (90% city). Open road i've recently done 7.4L down to CT.

As everyone says good service + filter change does wonders! I stick to OEM as far as possible though.

Interestingly, after "fonkong" to OEM BMW thermostat change, i noticed a big reduction in consumption. Also, coils seem to go at this mileage - might not have a HUGE impact on consumption, but the car runs noticeably better after these have been changed. Vanos seals are a must too!

Perhaps start with diagnostics to check for any major tell-tale error codes..? Goodluck

 

[Geoffro1]

Thanks M-thusiast, I would be delighted with your consumption of 10.5L!!