P**s poor fuel economy

[ItsAllAboutTheE30]

Does anyone have any idea why my fuel economy is so ridiculously low? I have a 325i sport and drive fairly conservatively. However, after putting in 45-50 litres the most I have managed to get out of a tank is about 170 miles.

When I bought the car a year ago the OBC said I was getting 18.9mpg, which I don't think it was, it now shows 17.9mpg. I know the OBC is probably inaccurate but 170 miles max. doesn't even work out to 17.9. At the age of 20 driving a sport this sort of consumption is starting to take its toll on my wallet, and preventing me from sorting out other things with my car. Any suggestions as to what could be causing this?

Cheers
Dave.

[fastdiablo]

Maybee Doris in your pic is resting her hand on the brake pedal while your driving ? ? ?

[sam325is]

join the club mate. mine cosumes that much and the engine is rebuilt aswell!! fuel system replaced inc all filters...its all new yet it still knocks it back. im averageing about 17MPG on the way to work each day. i was a 19 y/o college student when i bought my sport... but after driving a mk3 golf turd the fuel economy was better...they are true gas guzzlers... i have had 3 and i know that fo sho!!

[griff87]

I'm also 20 and drive a 325i, its got so bad (petrol at 108.9) that Im going to buy a cheap diseal and drive the e30 to enjoy it not as a daily drive. You throught about going diesel mate? (its a taboo subject on here) lol

[sam325is]

1.08 is only 10p more than the tolerable 98p per litre. so on a 25 litre fill up thats only £2.50 more.

So just chuck a couple of extra quid in to cover the extra cost.. its not masses more BUT it is annoying. and the price does need to come dfown. as soon as they broke the £1 barrier its been out of control!!! extortion

[griff87]

But last summer it was 90odd p per litre, so thats a fiver more per 25 litre fill up, and most people usually put more than that in. Personally if I find it cheap (waitrose, shell have proven to be good) I'll put loads in because I know it'll cost me more at my local BP.

I think having a daily drive is the way forward and enjoying the e30 at the weekend.

In 5-8 years it will probabley be £10 a gallon

[sam325is]

nah it wont people arent going to take this s**t for much longer.

[jaistanley]

That does seem low though. With my 325i lump dropped into my iS shell (4.1 lsd) I was getting 28 to the gallon average at around 60% motorway cruising and 40% ragging. Thats calculated using miles from odometer and an excel sheet used to input all of my fuel purchases from receipts. To be honest I was really surprised!

That being said, I've recently swapped to much shorter journeys and probably more like 75% ragging and though I haven't calculated it it's probably more like 20-22 mpg.

Have you tried servicing the ignition system (plugs, rotor arm, dizzy cap) and adjusting the tappets?

[griff87]

You say that, but nothing will actually happen...

Petrol will rise because of oil fields dimishing, political climates, Chinas growth blah blah blah. The only way its going to get cheaper is if dear old Gorden reduces the tax on it which I dont think he will.

People will keep buying it unfortunatley

Incidently: Gorden Brown was actually in my uni (swansea) on friday in my department, the ILS (institute of life sciences) unfortunatley I didnt have any lectures that day. Could of asked him about petrol etc if I'd known!!!

[sam325is]

oil fields arent diminsihing at all there is NO proof of that. saudi oil princes say there is no future shortage and even the head of BP says there is no future shortage. all propaganda mate.

8 months ago they found the biggest supply of oil ever found in one place and last week they found the 3rd largest supply in one place..both these places were in the america's.

antarctica is stil extremely unexplored and so are the america's anmd many other places. we dont know as much as we think we do. i dont know why people think its acceptable to turn speculation into fact. i remember my geography teacher tellimg me in 200 that in 2005 there would be no oil left.

the stone age didnt stop from lack of stone! the bronze age didnt stop from lack of bronze! the coal age didnt stop from lack of coal! and the oil age wont stop from lack of oil!!!


sorry off topic or what!!! yes 17.9 MPG it is a little low

[jaistanley]

I agree..

Make the Earth your bitch.

Pour oil on a duck.

[danman2k]

is there any difference in economy when using bp super expensive petrol compared to asdas own kind of thing. i use asda petrol and have got mine upto 21mpg now. im thinking of sticking a tank of bp expensive and seeing what i get then.

[jaistanley]

I doubt there'll be much difference at all. The calorific content is about the same. Modern engines yes. They have knock sensors and as such the ignition can be advanced farther with the higher ron fuel before knock occurs. The M20 just isn't advanced enough.

[edit] you could always re-map your car for higher RON fuel; but then you'd always have to run the more expensive stuff unless you had an ECU with switchable maps.

[danman2k]

I doubt there'll be much difference at all. The calorific content is about the same. Modern engines yes. They have knock sensors and as such the ignition can be advanced farther with the higher ron fuel before knock occurs. The M20 just isn't advanced enough.

[edit] you could always re-map your car for higher RON fuel; but then you'd always have to run the more expensive stuff unless you had an ECU with switchable maps.

sorry for jumping in the thread, thanks. maybe a zone chip for £70 bucks i think for better economy. im still mulling over it. thanks

[ItsAllAboutTheE30]

Yeh it is still very low Jai. To start with I thought it was just the bigger engine couple with an older car. That was until I read some of the many economy posts on here, and spoke to Si at his house a few weeks back, discovering other sports were returning over 220 miles out of a tank. I do, do shorter journeys to work, but it's probably a 60/40% short to longer, and generally I only drive fast where its appropriate.

Unfortunately Jai I'm a bit of a muppet when it comes to mechanics, my knowledge isn't that great so I haven't checked any of the things you mentioned. I'm working on improving that though, helps to be able to do things yourself when you own an E30. Any tips on how to check?

Dave.

[sam325is]

figured out why mine says its so low on the obc...its becuase the instrument cluster mpg gauge goes to zero for some reason as i come to stop meaning whilst im at lights the avergae MPG is going down and down and down even though my car is idleing like normal. so im probably getting very good MPG. you might have the same problem

[jaistanley]

220 miles to a 325i tank??

I used to be able to get 250 miles (270 - 300 when it was a 1.8 iS) from the smaller 4 pot tank in my car with the 325i lump and the 4.1 lsd.

Nowadays it's more like 200 because of the shorter journeys.

That said I can get it waaaaaaaaaaaaaay lower with a heavy foot. I swear I can see the petrol needle moving down when retarded subaru drivers annoy me..

A friend has a MAF conversion on his M20 (that has been serviced to within an inch of it's life too) and says he actually gets pretty good fuel economy considering.

I'm hoping to get some good figures when I install my S50. Here's to hoping eh? LOL

[Brianmoooore]

becuase the instrument cluster mpg gauge goes to zero for some reason as i come to stop meaning whilst im at lights the avergae MPG is going down and down and down even though my car is idleing like normal.

??? When your car is stationary, with the engine running, it IS doing 0 MPG.
If you remained stationary for long enough you would use all your fuel and have travelled zero miles.
Similarly, when you are driving along, and lift off the throttle, the over run fuel cut off kicks in, you are covering miles, and are using zero fuel, so the gauge is hard the other way.
If you continue with no throttle until the revs drop to around 1500 RPM, you can see the gauge start to show a high MPG reading, but not infinite any more, as the fuel cut off switches off.
You should be able to get around 26 MPG from a 325 under any normal driving conditions, unless you spend hours each day in stationary traffic.
Anything less, then you have a very heavy right foot, a fuel leak, or a sick engine.
If you find a 325 too expensive to run, then three letters will provide the cure: LPG.

[sam325is]

yea when im stationary the mpg goes to 0 not every time but sometimes. my mpg readings must be faulty becuase the car isnt doing 0 mpg when stationary.

when i start to drive the mpg needle does its reading correctly. stay at around 30 mpg ish.

when i stop at lights its 50/50 on wheather it will show 0 or 50 mpg

[BMracing]

my mpg readings must be faulty becuase the car isnt doing 0 mpg when stationary.

There's a problem somewhere if it says anything OTHER than 0 mpg when you're stationery. How can you be getting any miles per gallon if you aren't moving?!

I too get fairly poor economy from mine, probably around 150 miles from a tank. It's really because of my 3 mile journey to work and back, it's running cold most of the time. I've no reason to suspect a problem with it though, no running issues or leaks, and I can get over 400 miles from a tank on a longer run.

I remember Brianmoore saying that another advantage of running LPG is that it doesn't need enrichment when running cold.

[sam325is]

it should be past the 50 mark not on 0 at the other end!!

[grantfk10]

I reckon, on average, I'm getting around 380 miles to the tank in my cabbie so looks like I can't complain!

Bearing in mind I have a 54 mile daily round trip for work, and don't sit in traffic very often I must be doing ok, although it did hurt when I stopped at the local Morrisons (cheapest around here) for petrol and had to cough up £53 .

[jaistanley]

Yea short journeys are a bitch in mine too..

I though you ran on petrol till the car warmed up then switched to LPG? Not sure why mind - I'm no expert on LPG!

[Brianmoooore]

I though you ran on petrol till the car warmed up then switched to LPG? Not sure why mind - I'm no expert on LPG!

I always use petrol for cold starts (because it starts instantly, without having to draw LPG through the inlet tract), and then change to petrol within a few seconds. Any warm starts during the day are made on LPG.
The reason behind the idea of not starting on LPG, is that vapourising LPG takes large quantities of heat from the coolant, and if you try to use too much power right away, you run the risk of freezing the coolant in the vapouriser.

[Chase007]

figured out why mine says its so low on the obc...its becuase the instrument cluster mpg gauge goes to zero for some reason as i come to stop meaning whilst im at lights the avergae MPG is going down and down and down even though my car is idleing like normal. so im probably getting very good MPG. you might have the same problem

That is what my car does i am sure it is only because u r not driving so it has nothing to calculate as ur not moving?

[78dude]

If you think your Beemer is using a lot of fuel you should first take a look on the driver... If you floor it every time you access the motorway the 6-pot under the hood get thirsty.... I can manage 28mpg if I drive nice with my E34 530 Touring and that car have a V8 engine! If I start to drive it like I have stold it, I maybe get 12 to 15mpg

[sam325is]

nope it sould be right back at the 50 MPG end NOT the 0MPG end... thats what messing up my obd MPG Average.

any ideas what it could be anyone?

[dann-p]

Just got 250 to a tank on my 320 doing mostly 4 mile journeys to work and back.

Be interesting to see what I get on a nice long run to the Nurburgring in June. Won't be nice to see what I get on the ring itself though!!

[ItsAllAboutTheE30]

Thats the thing I don't have a heavy foot at all. My driving style has not changed since I have owned the car this past year either. Generally im quite conservative, due to the fact that 6 pots are thirsty buggers. I have fun when its appropriate, but my driving style really doesn't represent the consumption I am getting.

I do leave my car to warm up every morning for around 10 minutes, just to get it out the blue. Could this be causing such low mileage?? I have no fuel leak to my knowledge, so I'm guessing there is some underlying problem.

When people say they are returning 20 mpg or more on a mix of short and long journeys, and im getting less than 15mpg doing the same, it leaves me a bit concerned.

[aceraf]

I do leave my car to warm up every morning for around 10 minutes, just to get it out the blue. Could this be causing such low mileage?? I have no fuel leak to my knowledge, so I'm guessing there is some underlying problem.

I'm sure I've read that you're not supposed to leave the engine idling when first started.

I used to, but now drive as soon as i have started the car, making sure not to go above 2K untill it's warmed up.

If you're letting it warm up and then driving then it will consume alot more fuel.

[Simon13]

the blue temp sensor is probably shagged, i've got a 100% working spare if you want to try it for a week and see

my 325i ave 13mpg on track! if you really are getting that MPG then there is something wrong like brian said driving style or the engine.

[Spion]

Did a test on my 320i touring recently. Got 30 mpg driving carefully on the motorway, 28mpg with no regard for the weight of my foot on the pedal. Got 24mpg on local driving. It has an Evolve chip fitted

[ItsAllAboutTheE30]

Yeh that would be good Si nice one. Have to pop round yours again at some point, if you don't mind that is. Hows the engine going ?

[Simon13]

it's in and running we'll see how it lasts!

[Chris]

nope it sould be right back at the 50 MPG end NOT the 0MPG end... thats what messing up my obd MPG Average.

any ideas what it could be anyone?

Sorry to put this so bluntly but you are wrong fella.

When you are not moving but the engine is running you are achieving exactly 0MPG

No forward movement but fuel being consumed
_______________________________________________

When you start the car in the cold, i have always been under the impression that it should be allowed to idle for no more than a minute or two, just to get the oil flowing etc, then driven gently until it starts to warm up.

By gentle i mean, dont rev it past about 2.5K and try not to let it labour to much in to high a gear.

Favorite, for the bad economy would be the blue temp sensor by the thermostat housing.

Do the exhaust fumes smell 'rich' when the car is cold? What about when it's hot?

Cheers
Chris