[confused.com]

Hi all, bear with me on this, I know this topic has been done to death a few times but hoping you can add directly to this thread.

My mpg is seriously pissing me off now, I mainly drive the car locally and rarely through heavily congested areas, just your average type of town driving. *At best when i'm really nursing it I am seeing 23mpg, if I have a little hoon for a few minutes it will drop to as low as 20mpg!!!*

I've done all the known checks, the red *pipe is nice and clean as far as I can see BUT I've checked the engine temp on the hidden menu and it will get to approx 83 on a good run on the motorway, it will on get above 90 sat in traffic then move back down when on the move again. *I cant say for sure how long it takes to get 83 but nothing noticeably long.

Had it in for an MOT at Berry Chiswick a few weeks ago and the service advisor might as well have shut his eyes and put his fingers in his ears, he wasn't interested at all in hearing about the temp not rising to approx 90 (where it should be) - he did get it on diagnostics, and showed me a little sheet with a few errors they cleared down, nothing engine related.*

My issue is what to do next, the car is under extended warranty but my local garages, berry Chiswick or park lane charge £180ph to check it over - the service advisor at Chiswick wasn't helpful at all, he suggested I manually calculate the mpg? He said I could bring it in again for further checks but I'm not about to be bent over and fed the same diagnostics spiel.

I'm really after some information from you guys, what's your mpg like in comparable situations? I reset every tank full and aslong as I remain in town and do not go on the motorway it will quickly find its way to the low 20 's -within ten mins or so.

Is this an issue? Is anyone able to advise what I should be doing next or what BMW should be checking for me? I'd rather not take it back to Berry, does anyone know of a good BMW garage/service advisor in London? *

This is really bugging me to the point of wanting to sell the car now, fair doo's if this is what it should do, but I feel it's really low - I'd rather lose a few more mpg and have an m3 - 335d s are a poor compromise!

[335DEE]

Check out my signature , I use this now as my onboard computer is pissing me off too , reckon it's a full 10mpg out. BTW the ave 30.7 below accounts for a full tank of hooning about. I expect it to rise significantly on the next tank

[confused.com]

Originally Posted by o0timbo0o

Check out my signature , I use this now as my onboard computer is pissing me off too , reckon it's a full 10mpg out. BTW the ave 30.7 below accounts for a full tank of hooning about. I expect it to rise significantly on the next tank

Thanks timbo, will check it out - my manual calculations have lead me to crap mpg too!

Was that all town work for that 30mpg tank? Or a fair bit of motorway too?

[dxb335d]

I only did down driving when I had mine, with some spirited driving I was averaging 18mpg for a long time.

On the motorway it could do 50+ but took major restraint and only really to prove a point that it can do it.

[jimmylad]

If you get chance get on a clear bit of dual carrigeway that is fairly quiet and level. Set the cruise to about 60mph & then reset the mpg readout. When I did this last time I tried it I got about 55mpg over about 8 miles. If you get at least 45 there can't be much wrong.

City driving really drops it ( especially stop start) but having said that I have been into derby today (more of a village compared to London) from where I live and got 39 mpg ( trying my hardest) but it is sunday. Always resetting the mpg & having a competition with the computer. I remember when I first got mine I was well disappointed with the mpg but as time went by I managed to learn how to get the best out of it economy wise.

Usually get minimum of 29mpg for school runs and more recently got nearly 40mpg from Henley on thames to the Mayfair car park on park lane (twice) for the jubilee weekend & get high 40's on a motorway run sticking to speed limits. I got 28mpg towing my caravan from derby to Henley & that weighs nearly as much as the car.

Also, I think there is a knack to driving a diesel ( not saying you don't have it) like coasting up to traffic lights & islands & feathering the throttle downhill etc which is pretty much my driving style 90% of the time but The other 10% makes up for it

Tyre pressures ok? I run mine about 42psi on non run flats.

[wheelie good]

If that diesel its awful

I get 24-25 mpg flooring it and 28-29 mpg taking it easy 335i

Sounds like you got major problems

[phil200tdi]

Sounds like you need a remap.

[NickP]

Originally Posted by o0timbo0o

Check out my signature , I use this now as my onboard computer is pissing me off too , reckon it's a full 10mpg out. BTW the ave 30.7 below accounts for a full tank of hooning about. I expect it to rise significantly on the next tank

You might want to adjust your sig, you have a Diesel V6 coupe listed on there...

[AlwynMike]

You MUST do a manual brim-to-brim check. And probably more than one or you'll get fobbed off if it is reading seriously low.

The OBC readout in mine is way out, as is o0timbo0o's too by the sounds of it.

Soon after I got my car (AUC) I took it back to have the telematics unit replaced and asked the $tealer to check the OBC out. They said it was in spec, but as I'd only had a couple of fills I couldn't dispute this. they did say to take it back if I had any other issues. So, guess what - before it runs out of warranty, it's going back in to be adjusted. My OBC usually reads mid-30's, with the manual checks showing low to mid 40's (I don't do commuting).

I understand that you can adjust the OBC using the "hidden menu" but I'm not going to resort to that until the $tealer has had a go at it.

Mike

[Gra]

That's some seriously low MPG. My worst MPG for a brim-to-brim has been 35.24, my best 37.25, so it sure sounds like something isn't right...

[335DEE]

Originally Posted by NickP

You might want to adjust your sig, you have a Diesel V6 coupe listed on there...

It's listed as L6 in my main page .. i've deleted the sig and tried again .. still says v6

**UPDATE** It should refresh at next fill up

[335DEE]

Originally Posted by Gra

That's some seriously low MPG. My worst MPG for a brim-to-brim has been 35.24, my best 37.25, so it sure sounds like something isn't right...

Is that ODB or Manual calculation ?

The E92 has 13.4 gallon tank ( as far as I can tell) and with an easy 500 miles to a tank gives roughly 37 mpg.(A large proportion is motorway and at speeds that flow with the outside lane traffic) I reset my OBD calc each fill up and it's telling me i'm getting 29 mpg which equates to 390 miles.
I have always been suspicious of the onboard reading hence why I started to do a manual calc.

As suggested before I have had some map issues which have now been addressed and have been doing some 'testing' hence why the value in sig is low

[dxb335d]

Originally Posted by Gra

That's some seriously low MPG. My worst MPG for a brim-to-brim has been 35.24, my best 37.25, so it sure sounds like something isn't right...

If your always commuting the OBC is reading High. Go into town for the odd trip it will still read high. Drop a couple of mpg maybe


If your constantly hammering it or in town. It will be very low.

[Bomber]

I do a mix of driving in town and rural and never really see a figure above 27mpg, I am quite heavy footed as well

[HighlandPete]

As jimmylad has suggested, running a steady trip on the open road, is one of the best ways to really see whether an engine is running peak efficiency and giving sensible mpg. An OBC reset and 'brim to brim' is the only simple way to see if the OBC is really near the mark.

All the comparisons around 'town' driving, mean absolutely nothing, as there are just too many variables to compare one car to another. For example, what defines town driving? Near gridlock, or a easy country town with little restriction? Could easily be a 10+ mpg difference from one to the other.

Just to put it in perspective, a city driver of a 330d/335d could be sub 10 mpg if the conditions are congested enough, (it has been recorded) without anything being wrong with the engine.

If a steady cruise (at legal speeds) returns poor mpg, then it is time to examine ECT more closely, as 83C is on the low side. Plus other issues, such as considering mileage against injector condition, EGR rates and the like.

HighlandPete

[confused.com]

Thanks for the input guys, i have a long trip planned this weekend on the motorway, will see how it goes then.

Can someone share the manual calc?

My tank is half full so will top up and wont be able to do a brim to brim before the weekend, how many litres is the tank? that i should use for the calc.

[335DEE]

First off you will need to brim the tank , it's the only way to get an accurate calculation as a full tank is a known constant and won't change .. trying to work it off just your mid tank fuel guage won't work very well, reset the odo or take note of mileage. Do your trip and then brim the tank again taking note of the number of liters you used. Convert the liters into UK ! gallons and then divide the number of miles on your trip by the gallons used.
Easier still .. sign up to that www.fuelly.com and manually put the info in .. that way you can track it on an ongoing basis.

Tank is 13.4 Gallons or 61 liters for an E92 but i'm not sure if the tank takes into account the fuel feeder pipe which probably holds a liter or too hence why brimming the tank is the only way

[acerboo]

it could be the egr valve my mpg went down considerably when that went

[COBRAEDWARDS]

just for info.
i do a mixture of town and motorway driving, but rarely short trips so the engine should always be up to temperature.
obc shows 36 - 37 mpg all of the time.
i'm not a slow driver and have the odd blast to clear it's lungs.

[briers]

Saw this thread before i went away on the weekend, to oxford, same location as OP.

Around oxford city centre it was low to mid 20's too. Never had an issue with efficiency or temps since buying the car.

On way to oxford, purely m-way it was low 40's which included a regen.

On way back reset on m-way, half of it was 50mph-60mph variable speed camera and the usual m-way speeds, although took it easy as i was very low on fuel and wanted to make it back to Stafford to fill up with v-power diesel. It seems to be vanishing from loads of shell's. And the gentler drive saw high 40's, i think 47 something.

Always get low to mid 20's around town eventually on average. So i'd say you are normal.

[Gra]

Originally Posted by o0timbo0o

Is that ODB or Manual calculation ?

My figures are all manual calculations. I don't trust the readout in the car to be as accurate (it's been saying 37.5mpg for weeks now).

I use an app on my phone to calculate it called FuelLog. If you have an Android phone the lite version is free to use. Well worth it! Takes about 20 seconds to input each fill-up and it does the calculations for you.

[AlwynMike]

Originally Posted by Gra

My figures are all manual calculations. I don't trust the readout in the car to be as accurate (it's been saying 37.5mpg for weeks now).

I use an app on my phone to calculate it called FuelLog. If you have an Android phone the lite version is free to use. Well worth it! Takes about 20 seconds to input each fill-up and it does the calculations for you.

You're well ahead of me Gra, I usually do the calculations in my head as I'm driving away from the filling station. Takes me a lot longer than 20 seconds though!!

Mike