335d - Sudden heavy fuel consumption

[sortedcossie]

I've held of posting this as I wanted to get some correct figures from receipts.

our F31 335d has started to use fuel heavily. So much so that our old E91 330d with the 6spd auto is better now.

Last two tanks for example:

Filled tank to click off, 390 miles driven 100 of which motorway, the rest mixed urban mainly 30mph zones. 51 litres to refill = 28.95 mpg. Trip computer stated 35.4mpg

Again filled tank to click off, 370 miles driven 50 miles on dual carriageway up to 60mph, the rest mixed urban mainly 30mph zones. 52 litres to refill = 26.93 mpg. Trip computer stated 32.9mpg


Other notes:

1) My usage over the last 2 years has not changed, for example once a week I do an 11 mile each way journey into Birmingham (for my sins) using the same route I've always used. Traffic is pretty constant. Once a week it does a 2 mile round trip, but it has done that since I've had it.

2) I do not hammer the car hard at all, it's in comfort 99% of the time.

3) Stop Start seems to work as expected, once oil temp up to 70 degrees after 5 miles or there abouts.

4) It's had EGR done twice, last time 12 months ago when consumption was constantly mid 30's around town.

5) Tyre pressures are bang on for 4 adults.

6) There are no warning lights, and our local indy did a code read - totally clear.

7) It's serviced at half the use based schedule, usually 14 months and around 5,000 miles.


My next step is to take it into our local dealer, it's under assured warranty still - i'd held off until our indy had done a code read. My concern is they'll just say no fault codes. But there is no way this is correct now, something has changed.

Anyone else seen or heard of this on "35" variants of a similar age (2016 car).

[danb79]

Wondering if it could be the stats are failing and not getting up to temp?

Deffo get the dealer to sort it if it's under warranty; don't let them know you've had an indy read the codes as they could try to wiggle out of any work!

When the F31 had a few issues; it all got sorted under warranty; I knew what the issues were, just played dumb when I took it back to BMW etc

[sortedcossie]

I had thought about the stats, when they started to fail on our E91 the heaters took longer to warm through - different system I guess, these are blowing warm air in a minute of running.

On holiday next week so looking to book it in when back.

[bigdom]

Have you lost power/driveability?

[E-bmw]

"Sudden heavy fuel consumption" you have lost 2mpg?

Hardly sudden or heavy is it?

The temperature drop from summer to winter will easily do that, especially in a diesel.

[JakeT]

E-bmw said:

"Sudden heavy fuel consumption" you have lost 2mpg?

Hardly sudden or heavy is it?

The temperature drop from summer to winter will easily do that, especially in a diesel.

To be fair, my 330i losing 2 MPG under the same usage will give cause for concern. As an example, the long term average fell by 0.5MPG. This prompted me to check, and I needed to service the rear brakes. The inner pad on the offiside was stuck and just dragging a little.

Admittedly it’s been a long time since I ran a diesel, so don’t know about the summer vs winter diesel difference.

[Richard-D]

E-bmw said:

"Sudden heavy fuel consumption" you have lost 2mpg?

Hardly sudden or heavy is it?

The temperature drop from summer to winter will easily do that, especially in a diesel.

He's lost 2 MPG over a few hundred miles. His post reads to me that this has been getting progressively worse and the figures given are just part of the drop in economy he has seen.

[danb79]

The temps currently are not enough to effect economy; it's barely gotten into low single figures and when it has, it's been a few times...

Still stand by that the stats could be the cause of this; exactly what happened to my 730D

The OPs car is under warranty; it needs to be sorted by BMW

[rottenegg]

bigdom said:

Have you lost power/driveability?

Probably the most important question ignored. Poorly O2, dirty MAF, sticking brakes, partially clogged MAP sensor (N57s are known for it), bunged up air filter etc etc. All manner of things to investigate.

And not everything is fault coded. Sometimes you need to actually do some diagnosis and not rely on a computer screen. I've seen codes on Fx platform in ISTA's error memory that generic readers don't even register, such as bad primary O2 measurements etc. Bad O2 sensors will obliterate mpgs, but will also obliterate part throttle acceleration if it's the pre-cat one.

[otolith]

It's obviously very driving style dependent, but that consumption looks poor to me. My F34 335D gets around 40mpg in normal use and low 50's on a run. Claims a couple of mpg more than reality on the trip computer.

[rottenegg]

otolith said:

It's obviously very driving style dependent, but that consumption looks poor to me. My F34 335D gets around 40mpg in normal use and low 50's on a run. Claims a couple of mpg more than reality on the trip computer.

That's pretty good mpg. What is your long term average since owning the car? And not off the trip computer. Calculated at the pumps. That is a lot more representative of the real world than "On a run" readings as "On a run" could be 37mph to some people, and 78mph to others.

[otolith]

rottenegg said:

otolith said:

It's obviously very driving style dependent, but that consumption looks poor to me. My F34 335D gets around 40mpg in normal use and low 50's on a run. Claims a couple of mpg more than reality on the trip computer.

That's pretty good mpg. What is your long term average since owning the car? And not off the trip computer. Calculated at the pumps. That is a lot more representative of the real world than "On a run" readings as "On a run" could be 37mph to some people, and 78mph to others.

I don't generally record actual at the pumps, but when I've checked it's usually been 2-3 mpg optimistic. Last fill up I did record, which was 443 miles, 52.67 litres, 38.2mpg. That was about 100 miles of motorway (with my other half driving, which somehow always results in lower mpg despite going no quicker) and the rest was short journeys in 20/30 zones. It claimed 41mpg. It will typically claim 42-43 for that kind of use. It will claim 55mpg on the 260 mile motorway journey I do on a fairly frequent basis, but in reality that is low 50's.

[rottenegg]

otolith said:

rottenegg said:

otolith said:

It's obviously very driving style dependent, but that consumption looks poor to me. My F34 335D gets around 40mpg in normal use and low 50's on a run. Claims a couple of mpg more than reality on the trip computer.

That's pretty good mpg. What is your long term average since owning the car? And not off the trip computer. Calculated at the pumps. That is a lot more representative of the real world than "On a run" readings as "On a run" could be 37mph to some people, and 78mph to others.

I don't generally record actual at the pumps, but when I've checked it's usually been 2-3 mpg optimistic. Last fill up I did record, which was 443 miles, 52.67 litres, 38.2mpg. That was about 100 miles of motorway (with my other half driving, which somehow always results in lower mpg despite going no quicker) and the rest was short journeys in 20/30 zones. It claimed 41mpg. It will typically claim 42-43 for that kind of use. It will claim 55mpg on the 260 mile motorway journey I do on a fairly frequent basis, but in reality that is low 50's.

That's quite impressive for a 300+hp, circa 1700kg car.

[otolith]

Yep. And also a four wheel drive car.

[sortedcossie]

rottenegg said:

bigdom said:

Have you lost power/driveability?

Probably the most important question ignored. Poorly O2, dirty MAF, sticking brakes, partially clogged MAP sensor (N57s are known for it), bunged up air filter etc etc. All manner of things to investigate.

And not everything is fault coded. Sometimes you need to actually do some diagnosis and not rely on a computer screen. I've seen codes on Fx platform in ISTA's error memory that generic readers don't even register, such as bad primary O2 measurements etc. Bad O2 sensors will obliterate mpgs, but will also obliterate part throttle acceleration if it's the pre-cat one.

Nothing i've noted TBH performance wise, it feels like it has the effortless torque it's always had. I considered sticking brakes too - it's had front disks and pads 500 miles ago, rears were checked and still have 10k plus miles on them - wheels were taken off and no binding present.

E-bmw said:

"Sudden heavy fuel consumption" you have lost 2mpg?

Hardly sudden or heavy is it?

The temperature drop from summer to winter will easily do that, especially in a diesel.

Sorry, I wasn't clear - the two tanks were just the last two fills to work out the actual litres used. Prior to that it had always done mid 30's locally when working out from a receipt.

I'm convinced something is amiss, i'm going to use this current tank until it's done 300 miles them brim it again so I have three figures to work from. Then i'll book it in to be looked at. No way this should only be doing under 400 miles on a tank, when it used to do best part of 475 on this same use cycle.

[sunnyb13]

Assuming it’s been serviced recently fuel filter etc all done?

Have you tried a diff petrol station? Perhaps lower grade diesel being pumped from the station…

Anything in the boot? Tyre pressures the same etc?

[rottenegg]

sortedcossie said:

rottenegg said:

bigdom said:

Have you lost power/driveability?

Probably the most important question ignored. Poorly O2, dirty MAF, sticking brakes, partially clogged MAP sensor (N57s are known for it), bunged up air filter etc etc. All manner of things to investigate.

And not everything is fault coded. Sometimes you need to actually do some diagnosis and not rely on a computer screen. I've seen codes on Fx platform in ISTA's error memory that generic readers don't even register, such as bad primary O2 measurements etc. Bad O2 sensors will obliterate mpgs, but will also obliterate part throttle acceleration if it's the pre-cat one.

Nothing i've noted TBH performance wise, it feels like it has the effortless torque it's always had. I considered sticking brakes too - it's had front disks and pads 500 miles ago, rears were checked and still have 10k plus miles on them - wheels were taken off and no binding present.

E-bmw said:

"Sudden heavy fuel consumption" you have lost 2mpg?

Hardly sudden or heavy is it?

The temperature drop from summer to winter will easily do that, especially in a diesel.

Sorry, I wasn't clear - the two tanks were just the last two fills to work out the actual litres used. Prior to that it had always done mid 30's locally when working out from a receipt.

I'm convinced something is amiss, i'm going to use this current tank until it's done 300 miles them brim it again so I have three figures to work from. Then i'll book it in to be looked at. No way this should only be doing under 400 miles on a tank, when it used to do best part of 475 on this same use cycle.

That's a bit odd in that case. The temperature hasn't dropped that much since summer to cause a drastic drop in economy, besides which, if it's a Euro6 model year like mine, it never really dips noticeably in economy until it's 0 degrees or colder.

Were the last 2 tanks from the same filling station? I think winter diesel has kicked in now? Not that it should make a huge difference tbh, but could just be bad fuel?

Have you got ISTA? You could try resetting the DME adaptations and see if it improves.

[sortedcossie]

rottenegg said:

That's a bit odd in that case. The temperature hasn't dropped that much since summer to cause a drastic drop in economy, besides which, if it's a Euro6 model year like mine, it never really dips noticeably in economy until it's 0 degrees or colder.

Were the last 2 tanks from the same filling station? I think winter diesel has kicked in now? Not that it should make a huge difference tbh, but could just be bad fuel?

Have you got ISTA? You could try resetting the DME adaptations and see if it improves.

It's odd, this current tank has solely been used on local 20 minutes journeys, no motorways, and I can already see from where the gauge is compared to the mileage that this tank will be sub 25mpg when I refill to the brim.

Last two tanks, and this one all from different forecourts, two Tesco and one BP.

I don;t have ISTA.

I'm going to do another 100 miles in it, refill, work out the MPG from the volume used then book it in with the three sets of figures. It's got to be booked in for that air bag recall so i'll get it looked at then.

[Pica-Pica]

rottenegg said:

otolith said:

rottenegg said:

otolith said:

It's obviously very driving style dependent, but that consumption looks poor to me. My F34 335D gets around 40mpg in normal use and low 50's on a run. Claims a couple of mpg more than reality on the trip computer.

That's pretty good mpg. What is your long term average since owning the car? And not off the trip computer. Calculated at the pumps. That is a lot more representative of the real world than "On a run" readings as "On a run" could be 37mph to some people, and 78mph to others.

I don't generally record actual at the pumps, but when I've checked it's usually been 2-3 mpg optimistic. Last fill up I did record, which was 443 miles, 52.67 litres, 38.2mpg. That was about 100 miles of motorway (with my other half driving, which somehow always results in lower mpg despite going no quicker) and the rest was short journeys in 20/30 zones. It claimed 41mpg. It will typically claim 42-43 for that kind of use. It will claim 55mpg on the 260 mile motorway journey I do on a fairly frequent basis, but in reality that is low 50's.

That's quite impressive for a 300+hp, circa 1700kg car.

Had my 335d for 8 years. Always around 42 to 44 mpg, summer/winter, local or distance. I did get into the low 50s a few years ago when there was a tanker strike or something, and I was doing 56-60 on motorways. I got over 620 miles on that tankful.

OP - Something is wrong. A 335d should get 40+, unless you are batting it like mad all the time.

[rottenegg]

sortedcossie said:

rottenegg said:

That's a bit odd in that case. The temperature hasn't dropped that much since summer to cause a drastic drop in economy, besides which, if it's a Euro6 model year like mine, it never really dips noticeably in economy until it's 0 degrees or colder.

Were the last 2 tanks from the same filling station? I think winter diesel has kicked in now? Not that it should make a huge difference tbh, but could just be bad fuel?

Have you got ISTA? You could try resetting the DME adaptations and see if it improves.

It's odd, this current tank has solely been used on local 20 minutes journeys, no motorways, and I can already see from where the gauge is compared to the mileage that this tank will be sub 25mpg when I refill to the brim.

Last two tanks, and this one all from different forecourts, two Tesco and one BP.

I don;t have ISTA.

I'm going to do another 100 miles in it, refill, work out the MPG from the volume used then book it in with the three sets of figures. It's got to be booked in for that air bag recall so i'll get it looked at then.

Yeah I had that done last week. No dramas. Not that it's a difficult job

It might need some monitoring of live sensor data to make sure it's all within spec still. Hopefully they'll find the cause and it's nothing major.