Diesel Software Update

[TeddyRuxpin]

On my usual trip from Cardiff to London (or the other way around) I usually drive for 'economy' and was seeing as high as 54MPG, but usually 49-52MPG. Now I can't seem to get over about 44MPG, usually about 42MPH.

My average MPG has gone down from 40+ to 34 (currently).

Obviously it's a bit colder at the moment, so I'm interested to see what it will be like in the summer when we're on normal diesel and the temperates are higher.

 

[wongl]

I didn't notice any difference to the mpg after the software upgrade to my C300h. But my software upgrade was listed as 'Powertrain software update' or something like this. So not sure if this is the same update?

 

[grober]

I didn't notice any difference to the mpg after the software upgrade to my C300h. But my software upgrade was listed as 'Powertrain software update' or something like this. So not sure if this is the same update?

there have been numerous software revisions to the hybrid drive/gearbox system- perhaps its one of those?

 

[merc07]

Is the 29.5 mpg you quote in your C350 ?, if so thats not good.

Yes, my 350.
On a Motorway run I would see 48-52. I did a run on Thursday, stayed under 60mph to see what I could get and it was 43.5..
19mph is actually quite good !
I have now put in an earlier ecu version so I will see how this goes...

 

[elan362]

my 2016 c250d was in the dealers a couple of weeks ago and had a couple of updates.
I one was a gearbox update and other was an engine update iirc
the car still goes into top (7th) gear at <70 mph in normal mode (but in sport, it needs to be doing about 80mph.

 

[ferg f]

Jesus a 10 mpg drop .

How old is the GLE and how long is that journey and types of roads ?

Its not even three year old and has less than 27k on the clock.

Its a 35 mile trip with no town driving, two small villages and onto the motorway! So mainly motorway you could say!

Between services (circa 9k miles) she was showing 38mpg for all her different roads/driving but can now only achieve very low 30's on a run!

 

[Tomham]

Don't let them get their hands on your car they will wreck it. It's not compulsory in the UK. They are trying to scare you by putting DVSA pamphlet in
with the letter. If your car goes in for a service instruct the garage not to do "the fix". They cannot do it without your permission.

If you feel its green then go ahead but think of all the extra
mileage incurred by the AA/RAC when they get called to yet another engine management light/limp mode Mercedes.

 

[Tomham]

Update. I see on the DVSA site that that a recall has been added today valid from 14 Feb 2020. It doesn't however say what it is.

 

[Mikesmith29]

I didn't notice any difference to the mpg after the software upgrade to my C300h. But my software upgrade was listed as 'Powertrain software update' or something like this. So not sure if this is the same update?

Exactly the same for my C300h no difference in mpg or gear selections. However I have noticed it goes in to a higher gear earlier around town and goes in to coast mode more.

 

[elan362]

my service sheet says
'Carried out Diesel engine control unit update'
Updated Powertrain Control Unit software"'

 

[cws196]

I had it done on my C250/OM651 and never saw any changes over 12months. However, it’s a generation later than the OM642 so possibly the more electronic control on the 651 means it’s better able to adapt - pure speculation on my part but I seem to recall the earlier VW diesels which had to be ‘updated’ suffered more with chewing EGR’s etc than later engines.

 

[mikrt]

My C220 cdi OM651 is booked in next week for a safety recall regarding steering column (I think), while booking it on the phone I was told it would have the diesel software updated at the same time.

I told them I didn't want that as it was mapped (a little while lie, it's being mapped in a few weeks), and receptionist said ok no problem.

I'll remind them when I drop it off and will see if they listen.

 

[wongl]

I'll remind them when I drop it off and will see if they listen.

If you are dropping your car off for the service, the service manager (or rep) will present a form for you to authorise by way of signing off. I suggest you cross off the work item listed to update the ECU and write above your signature that you do NOT want any service updates that changes the ECU firmware that changes the emission and/or fuel consumption.

 

[mikrt]

Thanks for the heads up @wongl,
Nice to be pre-warned.

 

[Farmer boy]

Had my s205 250d updated yesterday. Seems to drive the same but only taken it 12 miles in commuting time traffic so time will tell. I received a booklet about add blu and that A top up before the next service may be needed. Checked add blu gauge on dash shows full as you would expect after a Service but range now reads 7,000 miles instead of 14,000 for a full tank prior to update.
I will look at fuel consumption and compare it with my daily log that goes back 4 years. Should be interesting. Will feed back in a few weeks when I have some data. Somehow I think I will be saying less mpg, let’s hope it’s not a big impact.

 

[TeddyRuxpin]

I was under the impression that the euro 6 cars with adblue just start churning through lots more adblue, with less mpg hit, but could be wrong!

 

[Tomham]

Lets hope that rather than going down the VW route of just pushing all the crap back through the engine and causing all sorts of problems maybe they have decided
to drown the crap in adblue.
Not sure why MPG should then take a hit?

 

[TeddyRuxpin]

Yeah, I personally think it will just use more AdBlue too, but I don't have one of those cars.

 

[mikrt]

I am wondering though, would there be any benefit in letting MB update the diesel software, and then getting it mapped @ week later?

I have read that warm up time is quicker after update, that would be beneficial.

Or would the mapping completely alter everything, or maybe leave some unwanted downsides?

 

[merc07]

2012 C350 - ran the updated ecu for a while, 7th gear will not engage in 'D' until 73mph, DPF soot levels climb continuously.
Put it in manual and you can change to 7th at 53mph

Swapped back to an older version ecu, 7th gear engages at 53mph in 'D'.
Weirdly though, now and again the soot level drops with normal driving - not even while doing a regen.
So yes, more regens as it now takes less time to fill the soot level.

60mph in 7th = 1400rpm
60mph in 6th = 1600rpm

200 or +15% rpm, not a massive difference but enough to notice less mpg...how can they say the update won't effect mpg ?

So, if you get it remapped after the update, make sure they are able to change the minimum shift points for the 'D' mode.