MPG gone thru floor after software upgrade

[itsamomentintime]

hello all
just had a software upgrade to clear an EML warning but now, the MPG i am getting is barely around 30 around town, and around 35 on the motorway. Was previously 40+ combined.

its a 2018 T6, 150hp.

anyone else had a similar issue?

 

[Sasquatch]

Is that the actual MPG, or that which the GOM (Guess-O-Meter) in the dash is telling you?

 

[itsamomentintime]

GOM - however it seems fairly accurate, given the amount of fuel fillups i am now doing

 

[Ads_Essex]

Was it a VW software update?

VW and the rigged software

Hi Guys in 2017 i purchased a New California which i took in at 500 miles to have a tow bar fitted i watched the vehicle not being worked on for over an hour, when i asked i was told software update !!! i asked why and demanded it to be put back as it was and was told sorry cannot do...

www.t6forum.com

 

[itsamomentintime]

Was it a VW software update?

yes it was - was to clear a P20EE issue

 

[Sasquatch]

GOM - however it seems fairly accurate, given the amount of fuel fillups i am now doing

You need empirical data before drawing a conclusion. Do a few brim fills and do the maths the old fashioned way.

The GOM is hopless. One fill up it'll be bang on, the next 15% out with no rhyne or reason. A tarot reading would give you a more realistic figure.

 

[Ads_Essex]

There’s quite a bit on Fault Code P20EE but, as @Sasquatch says, it’s well worth establishing if the issue is true and also reoccurring.

 

[mmi]

the next 15% out with no rhyne or reason

Interesting you mention 15%...
The T6 ECU smooths out the extra bit of fuel in the DPF regeneration in the following (typically) 60-120 km by showing 15% worse MPG on MFD. Showing the real MPG during the DPG regeneration would be... . unconfortable... thus VW alleviates the anxiety by spreading the extra fuel used by DPF regens over longer time - to match long term MPG display.

[T6_measured] Fickle fuel consumption on MFD – encore

In March 2020 finally got the long-awaited ECU (Engine Control Unit) software update. Unfortunately it took a while to get a good chance to do some measurements to try to figure out what has been changed. So finally a few weeks back dusted the VCDS and collected all kind of intriguing data. The...

www.t6forum.com

Also might be worth to consider aerodynamic drag change along air density changes.
For example at +25C the density is 1.18 kg/m3 but at 0C the density is already 1.29 kg/m3– so 9% of more drag right there.

Actually one could expect a slight improvement in the MPG with the software update as it does DPF regens less often.

[T6_measured] NOx emissions, AdBlue consumption, DPF regeneration - Before and after ECU update

Introduction An update campaign for T6 EU6 diesel engines took place in 2019-20. Affected engines were on van of model years MY16-MY18, including some of MY19. For M1 class (passenger carriers, VIN WV2...) the update was an official recall. For N1 class (VIN WV1....) the update was not...

www.t6forum.com

 

[dubber36]

Wow. I've only ever considered the effect on colder air and increased density having an affect on combustion, never aerodynamic drag. Now I think about it, it too plays a big part.

 

[phazer]

Also worth noting that "winter" diesel doesn't give the same MPG as regular diesel so you'll naturally see a drop through the colder months anyway.

 

[DaveD]

Wow. I've only ever considered the effect on colder air and increased density having an affect on combustion, never aerodynamic drag. Now I think about it, it too plays a big part.

It's certainly thought provoking. I suppose it also depends depends how you use the van, somebody using an empty van at motorway speeds will be affected more by aerodynamic effects far more than somebody who carries a heavy load in mainly urban areas with a lot of 20 and 30 mph limits.