fuel consumption on my 325

[Tom-s]

hi there, would just like to know what sort of mileage people are getting out of a full tank with a m20b25, i get about 160 and it just doesn't seem right!

[suchy]

M20B25 lumps aren't efficient by today's standards! Plenty of past threads to read through giving the same answer!! You are not alone...

[dave525]

that sounds crap!My 320 auto cab does over 260 on a tank and they are supposed to be the most thirsty.

[Tom-s]

i do have a fairly heavy foot but sometimes i can just to about 10 miles and the fuel gauge will seriously drop! the previous owner said that he had it re-tuned but maybe this has caused over fueling? i really cannot think why its like this! always stinks of unburnt fuel

[Tom-s]

i do have a fairly heavy foot but sometimes i can just to about 10 miles and the fuel gauge will seriously drop! the previous owner said that he had it re-tuned but maybe this has caused over fueling? i really cannot think why its like this! always stinks of unburnt fuel

[suchy]

The B25 have thirst problems when driving around town and adding in a heavy right foot from time to time won't be helping, but hey these things are meant to be driven- you plant your foot and it's going to open the taps and pour the fuel in!!

Saying that it shouldn't stink of unburnt fuel though! Have you checked the blue sender is working properly and the signal is reaching the ECU? Could be stuck on cold start- would be one reason for too much fuel and crappy economy.

Another reason would be the fitting of one of those adjustable fuel pressure regulators- they're crap and don't work properly (just a possibility if the previous owner had it 're-tuned')

[Speedtouch]

Check the blue temperature sensor and that spark plugs of the correct type and gap are fitted.

[Gavla]

160 miles urban driving is about what I get.

I am slightly confused by the fact that as far as I am aware I have a 63lt tank but whenever I fill her up when the fuel light goes on I can only put 45 odd litres in. That and the fact that the range on my OBC tells me that I can drive another 90 odd miles...

[jamlid]

I think they do 55 and 63 litre tanks? Depending on which model you have? I may be wrong.

I thought mine was a 45l tank at first, so thought I was getting 35mpg when I first drove it home..

[Tom-s]

the blue temperature sensor raises an interesting point... i have recently changed this as my temp gauge has stopped working! But that did not solve the problem, so am i right in thinking that maybe the car is running on cold start all the time? as the gauge is always showing cold

[Osamam3]

Just to hijack your thread so a b32 is more efficient than a m20b5 ! I drove mine from Cornwall on £60 and that was hooned about most of the way ! Mpg so far is good ! About 35 to 36 mpg on the motorway at a steady 80 to 90 .

[Speedtouch]

The blue temp sensor tells the ECU the engine coolant temp; the brown sensor next to it feeds the temp gauge, so check the connections to it or replace it if necessary.

Also, check the brass nuts on the back of the temp gauge, as they often work loose.

[pony]

hi there, would just like to know what sort of mileage people are getting out of a full tank with a m20b25, i get about 160 and it just doesn't seem right!

200 miles if I am lucky from a Tech1. Most I got is about 230 miles from 55 litre tank.

[Nobby_N]

is the 230 miles Pony including using all the petrol in the tank?

[pony]

is the 230 miles Pony including using all the petrol in the tank?

Close to it I know I definitely done 220 miles
But mine also stinks of petrol
Great for the sound and sideways but heavy fuel consumption

[toby]

Fuel leak? Check under the bonnet and under the car with engine running. I've seen fuel pipes have a tiny hole and spraying fuel everywhere inside the engine bay - which quickly evaporates and leaves no trace of evidence (potentially starts a massive fire ).

[jamlid]

Would just revving the engine high in neutral show leaks or would the engine need to be under load?

[dave525]

We,ve just been to somerset in our 320 auto cab.It did 28 mpg on mostly 70 to 80 cruising.Why dont you do a brim to brim test to see exactly what mpg you are getting.I would expect around 20 in town and up to 30 on a run.

[Morat]

What does your OBC read for Fuel Comsumption? Make sure it is set to M/G or you'll be looking miles per US Gallon or litres per 100km.
I thought my 17-18M/G average was OK until I started to pick up a misfire. The misfire got worse until I had the blue temp sender replaced which fixed the hot start issues but the idle was still bad until I checked the HT leads. They were aftermarket crap and two had broken down. I replaced them with good second hand leads and the car now shows 22 M/G on the OBC I can get about 250 miles from a 62 litre tank (brim to light) if I'm not booting it.
Take your fuel can and go drive a full tank until the fuel light comes on, 99% of the time they're far more accurate than the gauge itself. Fill it to the brim again and work out the mpg here:
http://www.torquecars.com/tools/uk-mpg-calculator.php

I always make sure there's exactly 5litres in the spare can. Firstly because the rest is meant to be an air gap so the can stays safe in hot weather and also so I can chuck it all into the tank and still work out mpg. I'm sad

[Speedtouch]

I thought I was just sad like that!

Except, to really do it properly, you need to run the tank to empty*, then work it out, as the low fuel level light tends to come on at varying degrees of emptiness.

* Cue all the doomsayers, going on about how you should never run the tank to empty due to sucking up debris at bottom of tank, etc...

[Morat]

Well, if you brim the tank, reset the trip, drive XXXmiles and then brim the tank again the figure on the pump will tell you how many litres you used to cover the miles showing on the trip. The only variables are the accuracy of the pump (you can use the same one if you're super sad) and the fill level. It should be pretty accurate

[dave525]

you dont have to run it to empty,fill to brim.Reset mileometer to zero.Run for half a tank.refill tank.divide distance covered by quantity of fuel used gives consumption. simples

[Speedtouch]

Except you'll get an artificially low fuel consumption figure, as the poor car is having to lug about a full tank of fuel...

[hongkongfuey]

Check your ecu maybe there is a non standard chip in it?

[hongkongfuey]

Check your ecu maybe there is a non standard chip in it?

[dave525]

Except you'll get an artificially low fuel consumption figure, as the poor car is having to lug about a full tank of fuel...

i wouldnt think it would make too much difference.At least you know its the worst you will get.

[dave525]

Except you'll get an artificially low fuel consumption figure, as the poor car is having to lug about a full tank of fuel...

forgot to say ive got one of your chips in my 320 auto cab.It did 28 mpg with two passengers,a full boot and started with a full tank.

[Sanchez]

This makes me feel good about getting 200miles from brimmed to half a tank on the gauge. 35mpg on a run. But my wife did mention I drive like a grandad!!!

[Speedtouch]

Except you'll get an artificially low fuel consumption figure, as the poor car is having to lug about a full tank of fuel...

forgot to say ive got one of your chips in my 320 auto cab.It did 28 mpg with two passengers,a full boot and started with a full tank.

Good to hear that, dude! Not bad, considering the official average fuel consumption figure for these was 26 mpg, which was about what I used to get out of my two L-Jet 320i's.

[jas025]

Mine was appalling the other week (about 13mpg) but mainly very short journeys and I also isolate the battery when it's not in use and a couple of people have said that doesn't help as the ECU needs to relearn how the engine's performing (or something).

Got 25mpg going to cranleigh and back - much happier with that.

How long does it take for the ECU to settle in if the power's been cut? Could that help explain some of the poor figures people have had?

[bmw9818]

off £20 i get around 60 miles urban, fast driving, if i push it 70

[Speedtouch]

Mine was appalling the other week (about 13mpg) but mainly very short journeys and I also isolate the battery when it's not in use and a couple of people have said that doesn't help as the ECU needs to relearn how the engine's performing (or something).

Got 25mpg going to cranleigh and back - much happier with that.

How long does it take for the ECU to settle in if the power's been cut? Could that help explain some of the poor figures people have had?

It is true, that the ECU will need to re-learn its settings following a power outage. However, it should only take a couple of miles or so to establish a reasonable standard of running, so unlikely to affect the mpg by that much. If your 325i is only doing 13 mpg, something is seriously wrong with it, although if you were doing stop-start London driving, maybe that's about right...

[jas025]

Mine was appalling the other week (about 13mpg) but mainly very short journeys and I also isolate the battery when it's not in use and a couple of people have said that doesn't help as the ECU needs to relearn how the engine's performing (or something).

Got 25mpg going to cranleigh and back - much happier with that.

How long does it take for the ECU to settle in if the power's been cut? Could that help explain some of the poor figures people have had?

It is true, that the ECU will need to re-learn its settings following a power outage. However, it should only take a couple of miles or so to establish a reasonable standard of running, so unlikely to affect the mpg by that much. If your 325i is only doing 13 mpg, something is seriously wrong with it, although if you were doing stop-start London driving, maybe that's about right...

A mix of either rush hour driving over speedbumps and trundling round the suburbs.

Still - it's quite a shock when you fill it up and realise that you've gone nowhere and spent £55.

I think I suffer from the same problem as others on here as well - I never get anywhere near the capacity of the tank and the warning light's never come on either even though it looks pretty empty according to the gauge. At 22 years old it's probably one of the bits on the car that I wouldn't trust to be accurate or work (a bit like the windscreen washer empty warning light - a truly annoying pointless thing - already replaced, now bypassed).

[jonny323i]

I went to the German show this year in my 325i Tourer which is about 210 miles each way for me and I did it on a full tank plus about £10 just to make sure I didn't run too low averaged 33mpg and around town inc planting the pedal a bit 23-24mpg on a zerod trip