Technical 17.8 MPG!! How come?

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Technical 17.8 MPG!! How come?

Oct 4, 2007
I thought the B was drinking the petrol down at a fearsome rate so I worked out the MPG.

227.2 km (141.2 miles) took up 36.02 litres of the stuff, which according to this calculator makes it 17.8 MPG (6.31 km per litre, 15.8 litres pre 100 km) :eek:

I don't drive like a granny, but nor do I drive like a maniac. I just drive pretty averagely I think. I got the exhaust changed at DTR a month or so ago, and the bloke there told me I needed the variator changing, saying the main problems I'll see is the infamous rattley engine and more fuel consumption. Surely the variator wouldn't affect the consumption as much as my figures would suggest though, would it?

When I bought the car a couple of months ago I drove it back from Wales and the fuel went down at the normal rate I would expect. So the car was OK then and the variator would have needed changing then aswell so I'm minded to think it's not the variator that's causing this. I only really noticed the increased fuel consumption about the time the exhaust got changed. Surely there's no way the new exhaust could affect fuel consumption is there?

Anyone have any ideas..? Much appreciated :worship:
It really depends on where the variator has stuck. If its in the full open possition then it is actually pretty normal that you burn 15lt/100km. Another factor is, driving "avarage" with a stuck variator means that you will almost double the normal consumption.
Try this, top up the tank, drive 100 miles like a granny (that is never go over 3000rpm and use 1 gear more in down hill) then top up the tank and make the math again. if you measure something like 10lt/100km it means that the variator is stuck the least wrong way(as far as fuel consumption). The more that number increases, the worse the situation is.
In any case, since it is a fact that the variator is for change, do it. By keeping it there, fuel is the least harmful thing you are "burning".
I drive like a granny some times and like on excasy some other times. 9-10lt/100km is what i use.

Keep in mind that in your situation, even the slightest step on the gas means that most of that petrol is thrown away unused. so IMHO, its logic that you get the numbers you get.
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sjladopoulos, cheers mate, I'll definitely get it changed when my wallet allows it. The thing is, if it's the variator that's the main reason, wouldn't the car have consumed fuel at the same rate a couple of months ago when I first got it? The variator's needed doing for a while after all - the car's on 102,000km and it's never been done yet to the best of my knowledge. What I mean is it wouldn't suddenly have got far worse in the last 2000km?
Maybe the situation is just getting worse. :)
Any indications of a possible fuel leak? can you smell petrol under any circumstances?
I had a fuel leak right from the tank a year ago.(from a valve for the fumes located on top of the tank). Have a look around with the car on but standing, open the bonnet and inspect the fuel lines. Another thing is: turn the key to the point prior to ignition and try to hear the fuel pump. It sounds like a mosquito flying next to your ear and should last for about 5 seconds and then stop. If it doesn't stop it means there is a leak somewhere.
Other reasons for increased consumption could be:
1) low tire air pressure
2) stuffed up air filter
3) low oil level
4) chocked injectors
5) spark plugs(and cables)
6) bad fuel (change petrol station)
7) 100kg of useless junk in the boot :p
8) very dirty car (increases the drag! don't laugh!)
9) maybe your opinion on "average driving" would be "blood sucking" for the rest of us
9) anything else you can think of :)

Good luck and let us know what you come up with (y)
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If the airflow meter is not functioning correctly this will also stuff the mpg and make the car feel a little sluggish, a good bet would be to get the ECU checked/re-set - that should give an indication of where the issue lies. As sjladopoulos says the other common issues are dirty plugs, clogged air filter and gumed up injectors - all of which are easy to remedy yourself.

I have noticed that if you keep the car in the power band of 3.5k rpm or higher the mpg goes down quite a lot - 17.8 mpg seems VERY low, I was getting similar from a 4.0 Cherokee Jeep...... :eek:
If the exhaust was changed I would check the O2 sensor hasn't been knocked or unplugged but it would probably run like a bag of spanners if this was the case. Only sure way to check is by putting it on a Co meter, lots of unburned fuel passing through the cat may cause it to go as well so i would check sooner rather than later.

I get more MPG on the 3.5lt BM so it is low.
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If the fuel consumption has changed dramatically since the exhaust has been changed my first call would be looking into that. Exhaust can have a profound change in fuel consumption when done by people who are just welders on not exhaust specialsits even if they like to call themselves just that.

Even if it is not the exhaust itself it might be something that has been done when doing the exhaust. I wouldn't look into anything else before this has not been checked.
Thanks guys, will look into that aswell. Took it to DTR today to get the variator changed in the hope that would help. When I told them the MPG they said that even if the variator was stuck in the most "open" position I should still see late twenties MPG so that's not the issue. The air filter was pretty blocked up aswell, so I changed this. Got a few other bits and bobs done too, can't quite remember what - it's listed on the receipt which is downstairs in the car - and I'll see if it fixes or at least helps the fuel consumption. I've done half a tank since that I initially worked out the MPG, so on the way back from DTR I filled the tank up again. Got 20.8 out of that half a tank, so that's a step in the right direction I suppose :rolleyes:

I think I'll run through another half or full tank of petrol now all this work's been carried out, work out the MPG, then see what my options are.

I've taken all the advice on board anyway, it really does astonish me sometimes how generous and knowledgeable people on this forum are when it comes to diagnoses and advice :)
As Alan and Doc point out its a small but enthusiastic (and friendly) bunch - and you are part of it!!!! (y)