325i with M5 mpg

[alan325i]

thought my 325i was using alot of fuel, and this was confirmed when i fitted OBC.

Im getting 15.1 mpg. I have changed the airflow meter with a good one, but still same MPG.

Any ideas of what i can do to get the 24.8 MPG im used to

[Jon_Bmw]

Well firstly are you on the right MPG setting on your obc? there is an american and an english one. The american one comes up as mpg and the uk one MG i think. Its been along time since i worried about fuel consumption.

[Cloggy Saint]

Do you have the correct coding plug in the obc?

[e30_Turbo]

The OBC's function on MPG's is not a reliable source at all.

Best bet is to count miles and gallons and get the calculator out.

OBC's are cool for temp, date but the rest of the functions are way out these days.

According to mine I get 13.5 mpgs, which is way out, I only get 10mpg's now

HTH, Mark.

[alan325i]

well i put Ԛ£30 in petrol and get a whopping 140ish miles out of it

[kam-325i]

well i put Ԛ£30 in petrol and get a whopping 140ish miles out of it

That makes me feel better, i get about 180-190 of Ԛ£30.

I average around 25-27 Mpg

[deian]

is it an automatic? they always use more fuel, are the brakes binding? tyres at proper inflation level? another issue could be a faulty/dead oxygen sensor, but as some said before, don't believe the obc 100%, it's more of an estimation based on some logic, after say 15 years there will be wear and tear on what produces the logic for the calculation of the mpg.

i had a bmw before and it said i got 28mpg, i was quite happy with it, but just put a tenner in, note where the needle is before filling up and see how many miles u can get before the needle reaches where it was, do the same again, until you are happy u got a pretty accurate figure, then do the same with more fuel, till ur happy, maybe then u could maybe investigate further whether the obc is inaccurate, and how to calibrate it? (if possible)

hope that helps

[alan325i]

its a manual, but another thing thats wrong with it but not sure if this would effect it is that it takes ages for the temp gauge to get out of the blue.

Ages = say 50 miles and then it never ever goes even close to half way.

[Cloggy Saint]

Does the heater only blow cold air?

[Dan318-is]

if it takes ages to do that an the heating is on then you have the same problem i do, matrix pipes i think

[adamS]

MOst obvious thing to ask is how hard do you drive it?

140miles is good if you bone it everywhere!

[M5pilot]

I drive an M5 and the fuel economy is no different to a 325i. 18-25mpg around town and 30mpg on a run.

[alan325i]

thats driving it normally, harldy ever boot it now as otherwise id get about 10 MPG .

Blows warm air after a while, but can drive the car for over an hour for the temp gauge to get out of the blue.

Would this have anything to do with petrol consumption due to eletronics thinks the cars still cold so more petrol going to engine???

Going to change the thermostat this weekend see if that helps.

[Dan318-is]

temperature sender and afm are your best bets mate

[alan325i]

well changed the AFM from my old car which used to register on the OBC 24.8 MPG.


Where the temp sender?

[Stevin]

To me it sounds like the Thermostat is stuck open ?

with the cold running temps... I dunno if that would affect fuek economy though... but I would think it would, cause a car that isn't running at it's optimum temp usually uses more juice

[buster]

i used to only get 100 miles to Ԛ£20 so 150 miles to Ԛ£30.Same as mine really

[Templ8e30]

To me it sounds like the Thermostat is stuck open ?

with the cold running temps... I dunno if that would affect fuek economy though... but I would think it would, cause a car that isn't running at it's optimum temp usually uses more juice

Yep that sounds like the culprit.

The thermostat should be closed until the engine is up to around 90c, if it is stuck open it will take ages to warm up. This will also keep the engine temp sensor in cool water telling the engine management to enrich mixture for a cold engine (choke) and give crap MPG.

New thermostat on the shopping list, get one from a dealer to avoid hassle. Some GSF stats are a bit iffy

The BMW part number is 11531713040 and it should be about Ԛ£25, I'd get a new o-ring with it as well.

Cheers,

Iain T

[alan325i]

ok cheers, will change it this weekend and let you know

[Danstable]

Iain, my motor is still guzzling the juice since the engine swap, it guzzled it before but now it's just frightening! I've mentioned before that is smells very rich when running, still getting some odd smells too. Any ideas on what to check? Reluctant to get it tuned if there is a dodgy component in there, the tuning exercise would be useless I guess.

[Brianmoooore]

it takes ages for the temp gauge to get out of the blue.
Ages = say 50 miles and then it never ever goes even close to half way.

50 miles to get up to temp, and you wonder why it uses excess fuel....?

[chu346]

To me it sounds like the Thermostat is stuck open ?

with the cold running temps... I dunno if that would affect fuek economy though... but I would think it would, cause a car that isn't running at it's optimum temp usually uses more juice

Yep that sounds like the culprit.

The thermostat should be closed until the engine is up to around 90c, if it is stuck open it will take ages to warm up. This will also keep the engine temp sensor in cool water telling the engine management to enrich mixture for a cold engine (choke) and give crap MPG.

New thermostat on the shopping list, get one from a dealer to avoid hassle. Some GSF stats are a bit iffy

The BMW part number is 11531713040 and it should be about Ԛ£25, I'd get a new o-ring with it as well.

Cheers,

Iain T

I just put a new thermostat in and it gives the above symptoms

Not tried it for economy yet but it don't go to halfway on the temp gauge

Should I buy another thermostat??? (Yes it was from GSF)

[alan325i]

this really dont look good

well the guy i brought this car of said the guy before had head gasket done (6 weeks before he had it)

Now what i dont get, well thin i do is that the was NO thermostat in the housing, hence why it took forever to get out of the blue.

Now when warm it still chucks out white smoke from exhaust which leads to me to believe that water is exiting the head down the exhaust gonna have to keep a look out on water lose now that a thermostat is fitted.

this is the car in question brought off ebay

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

but then i did only pay Ԛ£650 for it, and do have a spare reconditioned head sitting in my shed

[Brianmoooore]

]I just put a new thermostat in and it gives the above symptoms

Not tried it for economy yet but it don't go to halfway on the temp gauge

Should I buy another thermostat??? (Yes it was from GSF)

Doesn't neccessarily have to go to halfway. Anywhere in the middle section well away from the blue or red sections is fine.
What is important, is that it gets there quickly, and doesn't move appreciably, whether it's idling, cruising around, or being driven hard.

[Brianmoooore]

this really dont look good

well the guy i brought this car of said the guy before had head gasket done (6 weeks before he had it)

Now what i dont get, well thin i do is that the was NO thermostat in the housing, hence why it took forever to get out of the blue.

Now when warm it still chucks out white smoke from exhaust which leads to me to believe that water is exiting the head down the exhaust gonna have to keep a look out on water lose now that a thermostat is fitted.

this is the car in question brought off ebay


http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

but then i did only pay Ԛ£650 for it, and do have a spare reconditioned head sitting in my shed

Well, you've found why it was using excess petrol.
Regarding the white smoke. Just watch the water level and hope.If it uses water ,then it's probably your white smoke.