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Discussion Starter · #1 ·
Hi Guys,

Ive just recently purchased my GLC and it has been nothing short of horrendous on fuel. We get around 17/18mpg around town and struggle to get 33/34 on a longer run.. I got around 290 miles to a full tank of diesel and that was driving it very sensibly.. Horrified to think what it will be down to when giving it a hard time 馃槀

Any help with this would be much appreciated.

Cheers
 

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Hi Guys,

Ive just recently purchased my GLC and it has been nothing short of horrendous on fuel. We get around 17/18mpg around town and struggle to get 33/34 on a longer run.. I got around 290 miles to a full tank of diesel and that was driving it very sensibly.. Horrified to think what it will be down to when giving it a hard time 馃槀

Any help with this would be much appreciated.

Cheers
I agree with stubax, you must have a problem, I used to get mid to high forties out of my 250d on a long run and i wasn't hanging around! Now in a 300d and not sure what that is like on a long run due to Covid, but on short journeys high twenties low thirties.
 

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Discussion Starter · #5 ·
Thanks for your input guys.. So its just back from the dealer and the only thing they could find is that the battery was faulty.. Which apparently was causing stop/start not to work and could possibly throw the fuel off when the car was being driven.. So they replaced the battery and low and behold... stop/start still doesn't work and still getting 18mpg in town 馃槀.

Is it possible the car is maybe stuck in a DPF regen? One of my friends had mentioned it as when they regen it hammers the fuel economy..

Getting those figures and that's me driving very carefully trying to get the most out of it but still just smashes through the fuel.. I was at 60mph the other night on a fairly level bit of motorway and it was only at 31mpg 馃槼 having nothing but bother since we bought the motor and tempted to take it back as list of faults just seems to be growing arms and legs.
 

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Hi
You must have an issue of some kind - I get 52mpg driving a steady 65mph on cruise control for an hour on the dual carriageway. I鈥檝e a 250d premium plus.
 

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Discussion Starter · #7 ·
What you getting around town?
Hi
You must have an issue of some kind - I get 52mpg driving a steady 65mph on cruise control for an hour on the dual carriageway. I鈥檝e a 250d premium plus.
What you getting around town? Cars going back in next week so hopefully they get to the bottom of it, it鈥檚 driving me mental
 

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Discussion Starter · #9 ·
will see what next week brings when it goes back in 馃う馃徏鈥嶁檧锔廡his is my first merc and at this rate it will certainly be my last
 

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We have exactly the same GLC, done 40,000 miles and getting high 40鈥檚 on long runs and low 30鈥檚 around town.

The Stop-Start function stopped working after 15,000 miles - which was great news as I prefer it not stopping 馃憤 So pretty sure this has no impact on fuel economy or performance.

I was originally under the impression there was a second battery to handle Stop-Start. But Forum member Toobad wrote an excellent Forum Post explaining that the GLC has what鈥檚 essentially a Capacitor under the passenger side footwell + instructions on how to replace it - if you really want it.

Hope this helps
 

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Discussion Starter · #11 ·
We have exactly the same GLC, done 40,000 miles and getting high 40鈥檚 on long runs and low 30鈥檚 around town.

The Stop-Start function stopped working after 15,000 miles - which was great news as I prefer it not stopping 馃憤 So pretty sure this has no impact on fuel economy or performance.

I was originally under the impression there was a second battery to handle Stop-Start. But Forum member Toobad wrote an excellent Forum Post explaining that the GLC has what鈥檚 essentially a Capacitor under the passenger side footwell + instructions on how to replace it - if you really want it.

Hope this helps
Hi tony,
I鈥檓 not actually too bothered about the stop/start if I鈥檓 honest, it鈥檚 just the fact the dealer trying to palm me off saying that鈥檚 the cause.. they had also said originally that what the car is getting fuel wise is normal which I now know is just lies 馃槀

but aye in regards to the batteries, they replaced the starter battery which apparently is to do with the start/stop and doesn鈥檛 allow the car to go into eco.. there鈥檚 definitely something wrong deeper in just hope they get to the bottom of it. I鈥檓 in a bit of rut as the garage I bought it from is so far paying for the repairs but at some point it will all come to a grinding halt 馃う馃徏鈥嶁檧锔 Even if I sat at 50 mph on a level road it wouldn鈥檛 go near 40mpg.. just seems as soon as the accelerator is touched it plummets 馃槴
 

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I think there must be a problem, you should be seeing better MPG.

D4zban; is your Engine Management software up to date - I only ever saw 50+ before the dealer applied an update during a service after which 45 is the best I've seen on a run.

Also - Cruise Control - I get better mpg with cruise off. With it on the car seems to rush up to traffic in front and then brake heavily. Driving myself I can anticipate this and maintain a more constant speed. Unless the road is clear and cc can hold a constant speed, I suspect i get 3-5 mpg more by switching it off. Doesn't sound a lot but that's actually around 10%!
 

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Discussion Starter · #13 ·
I think there must be a problem, you should be seeing better MPG.

D4zban; is your Engine Management software up to date - I only ever saw 50+ before the dealer applied an update during a service after which 45 is the best I've seen on a run.

Also - Cruise Control - I get better mpg with cruise off. With it on the car seems to rush up to traffic in front and then brake heavily. Driving myself I can anticipate this and maintain a more constant speed. Unless the road is clear and cc can hold a constant speed, I suspect i get 3-5 mpg more by switching it off. Doesn't sound a lot but that's actually around 10%!
Hi Neil,

The car is going back in tomorrow afternoon so hoping they get to the bottom of it. If I go onto the motorway and then reset the computer once at speed it maybe sit around 40mpg but only once doing that speed.. Again, as soon as I come off the motorway the figures just tumble rapidly. I have been driving with a very light foot and it just doesn't seem to go above the figures ive mentioned previously. I took the car out a run today, mixture of town and long open roads(sat at 50mph for around half this mileage) and it only went as high as 29mpg before tumbling back down to 22mpg once I came back into town. We are getting around 20 miles to each bar of fuel, which will work out about 240 miles to a full tank.

Mercedes said last week that this was normal but no way im accepting that, I know the figures they publish are a crock of S*** but im miles off what you guys are getting!

Cheers for your input as all this info is helping me build a case against them.
 

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Have a look at the Fuelly website, they compile real-world data on various Mercedes models. Just be sure to select UK in the Units box so you will get British MPG and not American MPG with their smaller gallons.

Fuel Consumption Website
 

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Discussion Starter · #15 ·
Have a look at the Fuelly website, they compile real-world data on various Mercedes models. Just be sure to select UK in the Units box so you will get British MPG and not American MPG with their smaller gallons.

Fuel Consumption Website
I鈥檝e had a look on there but they don鈥檛 have GLC 250d on there, however the glc 250 petrol on there is still better than we are getting 馃槀

just spoke to the dealer and they are saying that when they are looking on the trip computer it鈥檚 because we are doing short trips.. regardless of the trips we鈥檙e doing 20mpg is still rediculous 馃う馃徏鈥嶁檧锔 I鈥檓 about at the end of my tether with them can see the car just staying with them.
 

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I would agree the fuel consumption of the 250d should be a lot better than the petrol version. Since MB removed their emissions defeat software some 4400 miles ago, my 2016 220d has returned 38.1 mpg according to the trip computer. Immediately prior to that it was reporting 43.5 mpg. It is not unfeasible could have been over-reporting. The only true way to ascertain your mpg is brim-to-brim filling and then manually calculating the fuel used over the distance travelled. I've got to agree 20mpg is outrageous, there are W12 Bentley Continentals returning better mileage!
 

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Discussion Starter · #17 ·
I would agree the fuel consumption of the 250d should be a lot better than the petrol version. Since MB removed their emissions defeat software some 4400 miles ago, my 2016 220d has returned 38.1 mpg according to the trip computer. Immediately prior to that it was reporting 43.5 mpg. It is not unfeasible could have been over-reporting. The only true way to ascertain your mpg is brim-to-brim filling and then manually calculating the fuel used over the distance travelled. I've got to agree 20mpg is outrageous, there are W12 Bentley Continentals returning better mileage!
Yeah I鈥檝e been checking the mileage the old fashioned way also and the trip computer is pretty much bang on.. we get around 20 miles to each bar of fuel 馃槀 12 bars = 240 miles to a 66litre tank, it鈥檚 outrageous.. it鈥檚 getting dropped off tomorrow night and I don鈥檛 want it back until it鈥檚 sorted to be honest 馃う馃徏鈥嶁檧锔忦煒
 

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Discussion Starter · #18 ·
So the report is back from car being in again, and the service im receiving is absolutely awful from Merc at Newbridge.. They replaced the starter battery 4 days prior to it going back again, and they had charge the battery again as voltage was low.. No solution for this apparently after paying 355 for a new starter battery.. and also the start stop still doesn't work 馃槀 They told me their techs had it doing 50/60mpg as it should on real time mpg.. im assuming they had it going downhill and coasting and looked at the bar.. as when I took it in I got 31 mpg on a 20 minute motorway journey(average speed 40mph) .. their service manager then took the car home with him and says he was getting 43mpg however his average speed was 55mph, and he says he sat at 57mph all the way home.. So he's basically reset the computer whilst at speed on the motorway to try achieve the most out the car, which is still absolutely s***! They are saying the car is performing as it should, and just feeding me all sorts of lies and conflicting information now. Completely lost all faith in anything to do with them now as they are offering no help at all.. Also brakes came back red (urgent) after also being green 4 days ago 馃槀馃槀.. Leave it to the experts they say 馃

Going to be going through their customer service team just shorty and hopefully they can at least show a bit of decency about this situation. So far the worst car ive ever had. 馃憣馃徎
 

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Yeah I鈥檝e been checking the mileage the old fashioned way also and the trip computer is pretty much bang on.. we get around 20 miles to each bar of fuel 馃槀 12 bars = 240 miles to a 66litre tank, it鈥檚 outrageous.. it鈥檚 getting dropped off tomorrow night and I don鈥檛 want it back until it鈥檚 sorted to be honest 馃う馃徏鈥嶁檧锔忦煒
what happened - any improvement?
 

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Discussion Starter · #20 ·
what happened - any improvement?
Hiya mate,

So they didn't find any other faults other than the starter battery.. However the car is slightly better on fuel it would seem, don't know if its in my head though. The service manager took the car on a 100 mile round trip and only manage 43mpg out it, and that was resetting the computer once at 55mph and staying at that speed.. Basically all flat motorway driving. They aren't doing anything else with it basically even though I don't really agree with the way they have achieved that figure as its not realistic driving. It also doesn't fix the fact it seems to be guzzling the diesel as soon as its in town though.

The new starter battery that was replaced also needed charged again.. Even though again it was brand new. Apparently normal procedure for them 馃槀

Ive lost all faith in them to be honest as they have sent me a video of their mechanic saying he got 50/60mpg on a test run, then their manager says he got 43 as stated above.. and im still yet to see it go above 40. Such contradicting information im receiving.. They also said in the first health check that front brakes were amber, rear brakes were green.. Then roughly 60 miles later the car went back in to then receive another report saying all brakes are red and they strongly recommended that all of them are changed immediately.

Don't believe a word that's coming out their mouth now and just looking into see what my options are for returning the car to garage I bought it. Mercedes customer services also being absolutely no help at all so they will be getting a glowing report from me on their satisfaction survey 馃槀
 
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