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Discussion Starter #1
Hi,
I've had the 250d for 1 year and could get nearly 50 mpg on a long run when driving sensibly.
Since the recent service, I've noticed a 20% reduction, now only realising 40 if lucky. Any ideas before I go back to Mercedes?
 

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I've noticed that my petrol mpg has dropped with the onset of the cold weather, could this be a factor for you too?
 

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Discussion Starter #3
I've noticed that my petrol mpg has dropped with the onset of the cold weather, could this be a factor for you too?
Thanks. It could be that, although I had it during last winter and don't recall the low mpg.
 

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I do the same journey repeatedly. 2 years ago my 250d would manage mid-late 40's. After it's service incl software update i noticed that fell to 40-42. After this years service I suspect it has dropped again, but had my roof-bars on, so need to check without.
 

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I do the same journey repeatedly. 2 years ago my 250d would manage mid-late 40's. After it's service incl software update i noticed that fell to 40-42. After this years service I suspect it has dropped again, but had my roof-bars on, so need to check without.
I am following this thread with great interest. If the dealer is de-tuning the engine to meet some arbitrary govt regulations I’ll get my GLC serviced elsewhere. That is a significant (huge) drop in efficiency. I too am a nerd regarding how I drive and the average mpg per tank. If I had that kind of drop I would notice. My MPG is consistent all year around from sub freezing weeks in winter to 90 degree F weeks in summer.
 

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Maybe emission regulations and therefore engine software are different US v EU. If main-dealer serviced, they apply software updates, who knows what those do, and also difficult to prove a drop in MPG. EU/UK users, anyone else noticed a reduction in MPG, particularly diesel models?
 

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Mercedes were caught with their trousers down and the German government forced them to remove their emissions defeat software. Here in the UK this took the form of a mandatory recall to apply a software update known as SRPC 1838. Essentially MB programmed their engine control software to meet the exact requirements of the emissions and fuel consumption tests which take place under very controlled conditions and the resultant figures are used to help influence customers to purchase the car. However, they bear no relation to the real world figures. A consequence of the reprogramming in diesel-engined cars caused a significant increase in AdBlue consumption which in turn caused the various engine sensors to report a higher fuel consumption, a increase of 10% being typical in my case. However, I have no evidence to prove the pre-update fuel consumption was correct in the first place. Only by brim-to-brim filling and manually recording the fuel used for the miles travelled both pre and post recall, could I confidently say my fuel consumption has increased.

On a side note, MB were falsifying the emissions and fuel consumption figures back in 2016 when I bought my 220d Sport. There is now a class action in the UK for compensation due to their false claims. I've signed up as a claimant but it is expected to be quite a lengthy process before a Court decision is reached.
 

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2016, GLC250D 4 Matic AMG Sport Premium
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Hi All,
It seems a bit daft if MB have changed the fuel performance software and actually decrease the MPG. Surely a higher MPG would be more environmentally friendly than a lower one. :unsure::unsure::unsure:
 
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