Bad Fuel Consumption? - BMW Forum

TheDon · 02-04-2005, 01:42 AM

Hi

I was wondering if anyone might have an answer to the following, I recently just got my car back (1998 528ia Touring) from the garage (not BMW) were they performed a service, Filters, spark plugs etc etc. But since getting it back I am getting really bad fuel consumption. On a full tank of petrol I used to easily get over 750km but since getting it back I am getting just over 600km.

Does anyone have any ideas why this might be?

Even the distance remaining with fuel left, which the OBC reports is confirming my bad fuel consumption.

If anybody has and ideas I would really appreciate there input.

Thank you.

billB · 02-04-2005, 06:03 AM

First i would use the old fashion way to determine fuel consumption. Prior to high tech we used to fill up the tank to the rim. reset the trip odometer to 0; drive for say 100 KM (in your case) then fill it up again to the rim. How many litres? devided by your KMs. Allow a little room for errors as you may be off on how you fill up the car in both cases. Try to do it in the same gas station/same position/car tilting etc.

To be sure and for comparison purpose disconnect the (-) on battery to reset electronics (you may need radio code) do the same through the computer then compare both outcomes.
good luck
billb

sp0rky · 02-04-2005, 07:33 AM

Oh no.

My car has also been getting bad gas mileage lately and it's been hands down the WORSE problem I've had to deal with. It's super hard to find. It could be anything as dumb and little as a hard-to-turn pulley or dragging brake, up to bad injectors, fuel pump, etc etc.

It could just be coincidence that it started doing this after the shop, too, but it would be hard to say that because usually it happens gradually. Maybe you have a small leak on your hose if they replaced the fuel filter?

TheDon · 02-04-2005, 08:23 AM

Thanks for the replies guys.

Don't want to disscount the battery due to I can not find the radio code, which sucks.

So I have do it the old fashion why. Originally when I got the car which was only a few weeks agao, I actually picked it up in Germany and drove 950km approx with an average speed of about 200kph and on that trip I ony consumed approx 100 liters of petrol.

Since then I had a full tank on a few times were each time I have easly done over 750 km on.

I take the car in for service and get it back,I do a few small top ups, but I notice something is wrong to I fill the car up and after 500 km the petrol light is one. I do the same again and still the same.

So I know there is something wrong because this is a serious loss in km.

To anser the question about the the fuel filter I am not sure if they changed it, but I have checked for leaks, by parking the car in the garage over night on paper and then checking in the morning also I have had a good sniff around the car with my nose to see if I smell petrol but nothing (I had a pertol leak once in the past and from that I learned you can normally smell it)

I did read somehere in the forum that spark plugs can make a difference, can they make this bigger difference?

Also can you point me in the right direction for the fuel filter I can have a look to see if that is the problem.

Thanks once again for the replies and ssuggestions.

billB · 02-04-2005, 09:13 AM

Quote:

Originally posted by TheDon@Feb 4 2005, 03:23 PM
Thanks for the replies guys.

Don't want to disscount the battery due to I can not find the radio code, which sucks.

So I have do it the old fashion why. Originally when I got the car which was only a few weeks agao, I actually picked it up in Germany and drove 950km approx with an average speed of about 200kph and on that trip I ony consumed approx 100 liters of petrol.

Since then I had a full tank on a few times were each time I have easly done over 750 km on.

I take the car in for service and get it back,I do a few small top ups, but I notice something is wrong to I fill the car up and after 500 km the petrol light is one. I do the same again and still the same.

So I know there is something wrong because this is a serious loss in km.

To anser the question about the the fuel filter I am not sure if they changed it, but I have checked for leaks, by parking the car in the garage over night on paper and then checking in the morning also I have had a good sniff around the car with my nose to see if I smell petrol but nothing (I had a pertol leak once in the past and from that I learned you can normally smell it)

I did read somehere in the forum that spark plugs can make a difference, can they make this bigger difference?

Also can you point me in the right direction for the fuel filter I can have a look to see if that is the problem.

Thanks once again for the replies and ssuggestions.

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OK ask you mechanic what type of spark plugs he put in there; did you see the old spark plugs condition? Air filter etc. for the fuel filter look under the car on the drivers side you cann't miss it on a 528i

I doubt the leak scenario very much; if you have one you'll see/smell it!

TheDon · 02-04-2005, 09:28 AM

Seriously though would a wrong type/bad make of spark plug effect the fuel comsumption that much ??

I am losing over 150 km per full fuel tank approx since getting the car back?

sp0rky · 02-04-2005, 01:06 PM

Quote:

Originally posted by TheDon@Feb 4 2005, 09:28 AM
Seriously though would a wrong type/bad make of spark plug effect the fuel comsumption that much ??

I am losing over 150 km per full fuel tank approx since getting the car back?

[snapback]285749[/snapback]

thats about 91.5 miles per tank so no, spark plugs shouldnt have that big of an effect unless they totally suck and are not burning anything. That would be rather unusual, though.

billB · 02-04-2005, 02:00 PM

Quote:

Originally posted by TheDon@Feb 4 2005, 04:28 PM
Seriously though would a wrong type/bad make of spark plug effect the fuel comsumption that much ??

I am losing over 150 km per full fuel tank approx* since getting the car back?

[snapback]285749[/snapback]

The Don
Without going into details we, as always, try to stick to the basics. As such a proper spark plug function is essential otherwise misfires will most likely occur. This leads into poor engine performance coupled with increased emissions and possibly increased fuel consumption. This is the ABCs of spark plugs; now whether it results in a loss of 150KM or 122.998KM is another issue. The point is A. to make sure that these plugs were changed for real by the mechanic and B. the proper plugs were installed on the motor. Either way bad spark plugs can cause additional engine troubles such as hard cold starts, rough when idling, increases in fuel consumption and the release of unwanted emissions at inspection stations; to name only a few.
Further the failure of just ONE spark plug can mess up the life of a four-cylinder engine’s power output by almost 25 percent and can eventually lead to emissions which offend the olfactory senses of the guy at the inspection station thus a red sticker with 30 days notice on the winshield !

In sum: Make sure the right stuff is there. Once the ground of plugs is covered/eliminated; we will look at other possibilities for the increased consumption of fuel. Make sense?

regards
billb

Torque · 02-05-2005, 05:41 PM

And don't get those tripple or whatever plugs... get normal Bosch ones. BMWs have been proven to dislike the 'high-tech' spark plugs much more.

sp0rky · 02-05-2005, 09:45 PM

Quote:

Originally posted by Torque@Feb 5 2005, 05:41 PM
And don't get those tripple or whatever plugs... get normal Bosch ones. BMWs have been proven to dislike the 'high-tech' spark plugs much more.

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He's talking about a 1998 e39. They work fine with plat. plugs. Only the first gen m50s, m20s and m30s hate them so bad. I still prefer copper core, though.