[Watsey]

My journey patterns using my F31 330d are very consistent each week : a couple of of days of short journeys (~5 miles each way), a couple of long journeys (~100 motorway miles each way) and some weekend general running around. Long-term (2 years) and fill-up average fuel economy has been very consistent at 36-37mpg calculated using Fuelly. I always fill with BP Ultimate from the same station and add Millers Oils. Under normal driving, i.e. not caning it, mpg has not been affected by the MPPK nor the DMS remap.

Fuel economy has dipped considerably across the last two tanks of fuel : 29mpg on the last tank (calculated); 32mpg on the current tank (OBC indicated, and the OBC typical reads 1mpg low). Increased fuel consumption of ~20% is significant.

The engine seems to be running fine : starts first time, no smoke, no hesitancy, revs sweetly, seems to make its power and torque (according to the butt dyno).

I've removed the MAF sensor and it's completely clean - literally looks box fresh. Removing the oil filler cap shows the oil to be in good condition : no emulsification. Car is always main dealer serviced. Now at ~72K miles.

I have the Carly DPF regen upgrade and ran it last week. Only ~16g of soot recorded, all of which was indicated as burnt off after I used it to request a regen. All seems to be fine.

It seems too recent and short-term to be the effects of ambient temperatures and winter fuel. During the couple of winters the fuel economy only dropped by 2-3mpg. A couple of bad tanks of fuel ? Just one of those things ?

Carly diagnostics always throws up error codes, this time including 8011F9 PTC module, 930BB9 DTC fault, Central Gateway synchronisation CD0487, steering power supply 4823FC. The fault codes aren't consistent each time I run a diagnostic, so it's hard to determine whether any of them indicate an actual or long-term problem. None of these codes appear to be engine related.

Constructive suggestions welcomed for things to check. Anyone else seen a big reduction in mpg recently ?

[Kiddy1]

By any chance have you had your car in for a service etc? My 330d was always 39mpg+, BMW updated software etc and now it will not get above 34mpg and the average mpg reading seems ridiculously sensitive, it can vary by 2-3mpg over a 12 mile commute.

[Watsey]

Not been in for a service for a few months but the steering rack was replaced a couple of months ago and the car was software updated.

The thing that's confusing me is that the actual fuel consumption has increased, not just the OBC calculated consumption.

In the motorway, at 'brisk' speeds, the fuel gauge needle drops like a stone.

[Watsey]

Originally Posted by Lobb

BMW getting concerned their cars don't meet emissions standards?
On the bright side, great excuse to trade up to a 340i

Not even my man maths can justify the cost of losing/transferring the substantial mods to my car in favour of a 40i.

[Kiddy1]

Originally Posted by Watsey

Not been in for a service for a few months but the steering rack was replaced a couple of months ago and the car was software updated.

The thing that's confusing me is that the actual fuel consumption has increased, not just the OBC calculated consumption.

In the motorway, at 'brisk' speeds, the fuel gauge needle drops like a stone.

Mine was in for the exact same reason, a new rack! I can quite honestly say that since that day I have noticed the mpg has been terrible.

[robbiep]

Originally Posted by Watsey

Not been in for a service for a few months but the steering rack was replaced a couple of months ago and the car was software updated.

The thing that's confusing me is that the actual fuel consumption has increased, not just the OBC calculated consumption.

In the motorway, at 'brisk' speeds, the fuel gauge needle drops like a stone.

There was a 'non-mandatory' emissions update - a bit like the VAG situation, but not so bad.

When my car was last in for a service I informed the dealership in writing (handed in when I dropped the car off) that they did NOT have my consent to perform that update.

I wonder if it's what has caused the drop in economy you are seeing.

[robwils]

Originally Posted by Watsey

I have the Carly DPF regen upgrade and ran it last week. Only ~16g of soot recorded, all of which was indicated as burnt off after I used it to request a regen.

Can I ask what this is ?
I’d like a way of either forcing a regen or knowing when ones in progress so I don’t stop driving till its done.

Rob

[Watsey]

Originally Posted by robwils

Can I ask what this is ?
I’d like a way of either forcing a regen or knowing when ones in progress so I don’t stop driving till its done.

Rob

I've been using the "Carly for BMW" App for quite a while now, but only recently bought the DPF regen module. It allows you to do two things, fundamental y: check the soot and ash levels in the DPF (basically a further diagnostic feature) and also to manually request a regen. It's not a 'forced' regen as specific parameters have to be met in order for a regen to take place (engine and DPF temp; engine rpm I think), however, once you've requested a regen one will take place the next time the parameters have been met.

Carly will supposedly give a real-time update on the phone screen of the DPF progress, i.e. reducing soot/ash readings, but as my DPF was already pretty clean it seemed to go to zero almost immediately.

Monitoring a normal, i.e. vehicle-triggered, DPF regen would be impractical as you'd have to have the Carly OBD adapter connected the entire time you were in the car, have your phone connected continuously, and monitor the DPF levels as you drive. Not safe really.

I wanted to make sure that DPF regens and soot/ash levels were not being affected by the DMS remap, and it seems that DPF maintenance is operating as normal.

[JLR1969]

Originally Posted by Watsey

Not been in for a service for a few months but the steering rack was replaced a couple of months ago and the car was software updated.

The thing that's confusing me is that the actual fuel consumption has increased, not just the OBC calculated consumption.

In the motorway, at 'brisk' speeds, the fuel gauge needle drops like a stone.

Has the remap remained on the car?

Do we know what they change with the update

[Novakbmw]

Anyone else seeing this on their 330d and 430d .... don’t want bmw costing me more money and the car eating more fuel, is it costing more fuel though or the computer trip been changed to show it’s less efficient that what they sold it has ? Can computer software update mak3 the car drink more fuel?

[Watsey]

Originally Posted by JLR1969

Has the remap remained on the car?

Do we know what they change with the update

The DMS map was wiped by the BMW software update and I then had it reinstalled (part of the DMS service - 3 years support).

[Kal101]

Had my 335xd in for a brake fluid change and mentioned that my car felt sluggish in the hope they would update the software.

Since then have found the car to be more responsive although does seem to drink a little bit more fuel.

Personally I’m happy with the trade off.

May be partiallly due to the colder weather of late.

[Derrymilk]

My 420d now dropped into the 34’s today
Previous 320d ran at 43mpg

[Ross_T_Boss]

Must be something in the air, because I was a bit shocked at a late-night weds night, 95% motorway at 85-90 and returned 33mpg. The only other time I've seen it that low was a very early run along the M4 at at 120...

It was very cold, the car wasn't up to temp for about 20 miles, also wet and windy as hell. So far from ideal conditions. But still, about 20% increase... the car hasn't been serviced in ages, its due next month.

[Ian0304]

Originally Posted by Kiddy1

By any chance have you had your car in for a service etc? My 330d was always 39mpg+, BMW updated software etc and now it will not get above 34mpg and the average mpg reading seems ridiculously sensitive, it can vary by 2-3mpg over a 12 mile commute.

Would the software be updated automatically during every service? Mine averages 41 mixture/eco but has just had a major service so I’ll keep an eye on mpg and update

[Novakbmw]

My economy was down this morn8ng on a m40 90 mike run. Down by 4 mpg ....

It’s no where near it’s first service .... however I do need to take it in because the back windscreen doesn’t work in regard to heating and clearing it .

Will they automatically update the software when they are sorting the rear windscreen issue

As I don’t want that , it’s a 67 plate 3 litre diesel

[HighlandPete]

I understood it was only Euro 5 engines that are offered an 'emissions enhancement'.

I'm wondering if it is possible there is a necessary software update for the EGR valve/cooler issues. That could well change economy figures.

[Daftasabrush]

Have you by any chance changed your phone app from gas tracker to fuelly and synced your data across? If so, you'll probably find it's now measuring in US MPG not UK so you'll find your 29mpg is actually closer to 35, which tallies with what you're used to.

[Watsey]

Originally Posted by Daftasabrush

Have you by any chance changed your phone app from gas tracker to fuelly and synced your data across? If so, you'll probably find it's now measuring in US MPG not UK so you'll find your 29mpg is actually closer to 35, which tallies with what you're used to.

Yes, very recently moved from GT to Fuelly but I checked the settings and selected UK, so it's not that. The figures in my post are all calculated from refills, i.e. accurate data.

Given the extended periods of cold weather it could be the current draw for the ceramic interior heater placing a lot of load on the engine (warm air is typically available after just a couple of minutes of engine-on) but a 6-8mpg reduction would be huge if it was just due to the heater.

I typically get 450 miles to a tank. Currently 1/4 to empty and 266 miles on the trip. OBC indicating <31mpg, which in reality will be 31-32mpg brim to brim.

[Daftasabrush]

And there was me thinking I was being clever

[Watsey]

Originally Posted by Daftasabrush

And there was me thinking I was being clever

Thanks for the suggestion - could have easily been that.

Given there are no symptoms, it's a mystery.

[HighlandPete]

Originally Posted by Watsey

Given there are no symptoms, it's a mystery.

Have you checked the ECT, to see if the thermostat is functioning OK? Not a common issue like on the M47/57 engines, but worth making sure ECT is ~90C.