[satish_141]

Hi,

My 55 plate 320D is struggling to do get anything more than 36 MPG. The car was services about a month ago. It was doing 39.5 before the service and the recent cold spell, but now combined it only does around 36+ MPG. I drive 30 miles a day motorway and around 10 miles city.

Please let me know what could be the reason for suddent drop? anything that I need to get checked? any help appreciated. Thanks.

[kdiz]

That isnt a big deal of difference there. Bit more traffic, driving slightly faster, not being as conservative with the gears, tyres not at the correct pressure, more fuel than normal in the car, tyres not setup for colder temps.

So many things can effect it.

[HighlandPete]

Could well be just the colder conditions, 10% increase in consumption is well in range.

There is the possibility a thermostat (EGR or main) is causing low coolant temperature. You can access the hidden menu to see if the coolant temp is low. Some run less than 80-degrees. Ought to be around 90-degrees when heat soaked. Common for the EGR 'stat to fail. Will not be picked up in any service checks.

HighlandPete

[satish_141]

Hi kdiz, thank you for the response you may be right.

Hi HighlandPete, Could youu please send me steps as to how to access the hidden OBC menu to check the coolent temp? that will be helpful, thanks.

[HighlandPete]

Originally Posted by satish_141

....Hi HighlandPete, Could youu please send me steps as to how to access the hidden OBC menu to check the coolent temp? that will be helpful, thanks.

Just noted your reply... see you have asked the question in a new topic and a link has been posted by a forum member.

Check it out and see what you find.

HighlandPete

[Jeff123]

I have found that the 320d is only really economical if you drive in an economic style and get long, steady runs. Urban in winter with spirited driving gets me mid 30's at best.

Once you get the car warmed up and up to speed it's very good. Just feels like it will cruise all day at 85mph (45+ mpg).

[satish_141]

Hi Jeff, Highlandpete thank you both for responding!

[m1bjr]

Yup, thermal efficiency is key on the diesel.
In this weather they just dont get hot enough

Just began tracking mine below (see sig) but in Summer when new it was about 70mpg if kept below 70mph on a long run.

[satish_141]

Originally Posted by m1bjr

Yup, thermal efficiency is key on the diesel.
In this weather they just dont get hot enough

Just began tracking mine below (see sig) but in Summer when new it was about 70mpg if kept below 70mph on a long run.

70 mpg? That's a lot! Never heard any BMW doing that much?

[jonsteele]

I've had 70 mpg from mine on a long motorway run, driving like my granddad! Its possible, but its boring getting it!

[satish_141]

thank you all for the responses and the suggestions. With input from Highlandpete I managed to access the hidden menu and changed the correction factor to 925

37/40 * 1000 = 925

hidden menu - 20.xx - MPG correction factor

and then also I started to drive a bit more sensibly and with the temps back to double digits, my 320D is doing 44.5 on the motorway and around 40 town driving.

I am so pleased

[hems77]

Originally Posted by satish_141

thank you all for the responses and the suggestions. With input from Highlandpete I managed to access the hidden menu and changed the correction factor to 925

37/40 * 1000 = 925

hidden menu - 20.xx - MPG correction factor

and then also I started to drive a bit more sensibly and with the temps back to double digits, my 320D is doing 44.5 on the motorway and around 40 town driving.

I am so pleased

hi

how do you access the hidden menu? what is this setting for exactly and should i change it?

my 320d has been giving crappy mpg recently in the recent weather - around 34-36mpg. used to be around 40mpg.

cheers

[satish_141]

Originally Posted by hems77

hi

how do you access the hidden menu? what is this setting for exactly and should i change it?

my 320d has been giving crappy mpg recently in the recent weather - around 34-36mpg. used to be around 40mpg.

cheers

Hi,

Please find the instructions below:

http://e90.wetpaint.com/page/BC+hidden+menus?t=anon

[hems77]

Originally Posted by satish_141

Hi,

Please find the instructions below:

http://e90.wetpaint.com/page/BC+hidden+menus?t=anon

Thanks

Might take a look this weekend.

Can I just check though, which menu option do you change and how?

cheers

[satish_141]

Originally Posted by hems77

Thanks

Might take a look this weekend.

Can I just check though, which menu option do you change and how?

cheers

it is menu option 20.01, 20.02 and 20.03 but to get to menu 20, you need the unlock code which is in the first menu.

if for example your first menu says
KB145671
you need to add 1+4+5+6+1 = 17

this will be your unlock code which you need to enter in menu 19.00 to see menu 20.00

difficult to understand, but once you get it, it is easy

[E92westy]

Originally Posted by hems77

hi

how do you access the hidden menu? what is this setting for exactly and should i change it?

my 320d has been giving crappy mpg recently in the recent weather - around 34-36mpg. used to be around 40mpg.

cheers

My figures were 41mpg in the warm weather, dropped to 36mpg when it got really cold.
My commute is 20 miles each way and mainly urban.
Now it's warmed up a bit, I'm back at 41mpg.
I've checked my coolant temp and it gets to 88 degrees in about 8 minutes, so I think all is fine.

[satish_141]

Originally Posted by E92westy

My figures were 41mpg in the warm weather, dropped to 36mpg when it got really cold.
My commute is 20 miles each way and mainly urban.
Now it's warmed up a bit, I'm back at 41mpg.
I've checked my coolant temp and it gets to 88 degrees in about 8 minutes, so I think all is fine.

Mine is exactly the same issue, it dropped in cold weather and back to normal, at least we all need not worry next winter when it drops agian as we know the reason....this forum is simply too good!

[HighlandPete]

Originally Posted by satish_141

Mine is exactly the same issue, it dropped in cold weather and back to normal, at least we all need not worry next winter when it drops agian as we know the reason....this forum is simply too good!

I believe it is really the first winter many have found out what happens to modern engines in winter time.

Some of us have winters every year, so have a bit more knowledge of mpg variation. Personally I'd say we get best mpg in our diesels when the temperature is between 12 - 16 degrees. Experience from many different diesel engines, over many years. Plus up to a 20% difference (good to bad) over the exact same conditions, purely on temperature variation.

MPG spread for a particular engine, you can 'halve' or 'double' the consumption, (eg. 20 - 40mpg, 25 - 50mpg) over the variations and conditions we see in driving. All normal.

HighlandPete

[satish_141]

Originally Posted by HighlandPete

Could well be just the colder conditions, 10% increase in consumption is well in range.

There is the possibility a thermostat (EGR or main) is causing low coolant temperature. You can access the hidden menu to see if the coolant temp is low. Some run less than 80-degrees. Ought to be around 90-degrees when heat soaked. Common for the EGR 'stat to fail. Will not be picked up in any service checks.

HighlandPete

Hi HighlandPete,

I checked the coolent temp of my car after a 1/2 hout run and it is only showing 79 degree C! Do you think I need to get my EGR thermostat changed? please suggest.

[E92westy]

Originally Posted by satish_141

Hi HighlandPete,

I checked the coolent temp of my car after a 1/2 hout run and it is only showing 79 degree C! Do you think I need to get my EGR thermostat changed? please suggest.

There's been a couple of threads on BMWLand about changing EGR and main thermostats on 3er and 5er diesel...

http://www.bmwland.co.uk/forums/view...p?f=4&t=108791

.... for instance.

[satish_141]

Originally Posted by E92westy

There's been a couple of threads on BMWLand about changing EGR and main thermostats on 3er and 5er diesel...

http://www.bmwland.co.uk/forums/view...p?f=4&t=108791

.... for instance.

ah...thank you for the link...but I dont think I will be able to do it myself will take it to a garage instead..but I just need to be 100% sure that there is a problem and 79C is low and I need to change it..

[HighlandPete]

Originally Posted by satish_141

ah...thank you for the link...but I dont think I will be able to do it myself will take it to a garage instead..but I just need to be 100% sure that there is a problem and 79C is low and I need to change it..

That is low if you have plenty of heat soak in the engine. I personally would check again and get a second, even third reading. If the same, or similar, yes you are running low.

HighlandPete