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Discussion Starter · #1 ·
Hi, Just bought myself a 1999 BMW E46 318i SE.
There are a couple of issues that seem to bog me at the moment, the foremost being the poor fuel economy: 300 miles to tank in town, 400 miles all motorway, about 25-35 MPG I would say.
* Checked air filter, its newish but not BMW original, should I replace it? The air filter box was clean..
* Checked tyre pressure: All tyres 225/40/18 were quite low at 28. Checked quik-fit website. They advised 34 front, 42 rear, so changed that. However, I also have a set of 4* 205/60/15 spare BMW alloys. Should a change to them improve economy?
As this car is a rear wheel drive, should the better 2 of 4 tyres be at front or rear (in FWD cars, the better set goes to the front generally)..
* Fuel filter: Would changing the fuel filter help fuel economy?
For info, the oil filter and oil have been recently changed..

Also I've added the "injector cleaner" during last fuel refill.

If there are any other actions you could advise in addition to above, please let me know.

Thanks for your help in advance...
 

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air filter...if clean then should be ok afaik
tyres...you have a sticker on your b pillar that will advise correct pressures...its generally the same pressure whatever tyre size you run.
fuel filter...know if its been changed before? cant see it making any odds to your economy though

any idea of the lamda readings from your last mot?...may be running a bit rich if the lamda probe is getting old
 

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Discussion Starter · #3 ·
thanks 328mark, the idea of running slimmer tyres is to reduce friction and therefore improve fuel economy. The quik-fit site lets you enter your reg and gives tyre pressures per tyre size that you may have. I also do not like the harsh ride from the 225/40/18s.

Any idea about the better tyres to be at Front or rear of a RWD car mate?

Fuel filter, since the latest service history is missing, I can't advise. However, my mate is a mechanic and he took a look at the underside of car. When he came to fuel filter, he said looks like its never been changed, so change that. Now I didn't dare ask him how he could actually look at filter from outside and conclude, but if it helps fuel economy, I am up for replacing it. What do you think?

I've the MOT from Mar09, I will check if it mentions lambda sensor (same as probe?) readings. Is it difficult or costly to just replace the lambda sensor?
 

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rwd cars want the best tyres at the back...less chance of oversteer.
the fuel filter is cheap enough...go ahead and do it :)
replacing the lamda probe/sensor isnt difficult,but you do need a special socket (with a split for the wires) it'll be a whole lot easier if the car is on a ramp.iirc they cost around 80 quid
 

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I think tbh everything mentioned wont help the fuel economy apart from perhaps changing the lambda...

You would be able to tell if the fuel filter was changed, it would be very clear if it had been changed in terms of nuts etc looking as if they have been used a couple of times and dirt surrounding the filter housing itself would be a good way to judge.

But again this will only work if the car is running rich and 25-35 sounds about right to be honest. Dont forget that since petrol is costing a lot more these days it feels like you are spending more and getting less miles.
 

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Discussion Starter · #9 ·
craigledden, not just fuel economy, its do with a harsh ride as well which I am not too keen on really..
I've owned Focus TDCI, Astra DTi and Mondeo ST220 in the past few years and tbh, this one is more than twice expensive than to run any of these cars.
My astra which is fitted with all new features for a car, costs £35 a year to tax and returns 63 MPG approx combined on a regular basis.
 

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I have a 2000 318i E46 and to be honest 25MPG is reasonable to be honest. You shouldnt really be upset or be annoyed on that side of things.

If you really want to improve fuel economy go down to 15inch wheels change fuel filter put the standerd air box and filter in and change gear every 2000 revs.

But the car will look wank, you will have good fuel economy but its better to have a bit of modifying and loose abit of fuel consumption
I Personally added a simota carbon fiber induction kit proper ferrari sound really loud but drinks my petrol i drove 1 mile on the a20 and i lost 10miles on my clock went from 178miles left to 168 in one mile but im happy im ridding on AC Schnitzer Type V 225/40/18 all round Still smiling tho.
 

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Sounds about what I achieve to a tank, I normally brim it and run it down to the light, get 350miles ish.

Air filter has just been done so ill see if that makes a difference.

All I wish is that I went for a silky 6 pot instead! owell
 

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Discussion Starter · #15 ·
Bonse, i agree 330Ds are the best combination, however they are quite more expensive than their petrol counterparts.
For the miles I do every week, I would be happier with the 320d I think.
 

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Discussion Starter · #17 ·
bhalay, I would advise to change the air filter, clean air box as well with a hoover.
Also change the lambda/ O2 sensor should help is what I've been advised.

Air filter is very cheap, O2 sensor depends on where you source it from!!

What tyres do you run at the moment?
 

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Sounds about what I achieve to a tank, I normally brim it and run it down to the light, get 350miles ish.

Air filter has just been done so ill see if that makes a difference.

All I wish is that I went for a silky 6 pot instead! owell
i have a 2.8 and thats what i get from a tankful...just goes to show how overworked a 4 pot is pulling that heavy body around:cool
 

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bhalay, I would advise to change the air filter, clean air box as well with a hoover.
Also change the lambda/ O2 sensor should help is what I've been advised.

Air filter is very cheap, O2 sensor depends on where you source it from!!

What tyres do you run at the moment?
i've recently serviced the car, and changed all filters except the fuel filter which i hadn't got round too at the time. i've got some vredastein's on at the minute, two of which are brand new. is the 02 sensor easy to change?
 

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ive got a 2001 318i touring and i'll be lucky if i get over 30mpg. car is too heavy with such a small engine. mate of mine got 2002 330i and can get nearly 40 mpg if he drives at about 60ish( so he says)
 
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