2015 GLC 250d Prem Plus Fuel Economy

GeeJayW

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Apr 24, 2017
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NW Blighty
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S205 C250d AMG Line P+, MX-5 25th Anniversary Edition
Over the last 18-mile journey, which was just into town and back out our C-Class averaged 35.3 mpg
Since the last reset 15,000 miles it’s averaged 44.1 mpg
99.9% of the time we use C mode and in general tend not to push on too much as it can get through rear tyres in 8,000 miles.

Same engine (OM651) I would expect a GLC to be significantly worse on fuel than that. It’s a bigger, heavier car with bigger wheels and 4WD.
 
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CGillies90

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Feb 4, 2021
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Bathgate
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Mercedes GLC 250 d Premium Plus Night Pack
Even if you think car is running at correct temp if thermostat cable / sensor isn't working correctly then economy will be appalling. There wasn't any OBD2 error codes with mine. Unfortunately thermostats are silly money for mercs (mine I think was £192 on eBay for a genuine one without fitting - an e350d) compared to £20 for my old Jag and 10 mins to swap over myself. But this was the cause of my terrible economy with Terracleaning making it superb (for the moment)
I will have a look at what you have said mate.. seems to be sitting ok on the dash but I understand it could be off under the bonnet.. I thought about terra clean but again didn't know anyone who has had it done so that's good to know. I had the car out on a big trip yesterday and averaged 37mpg. 572 miles average speed 55mph so was literally all motorway sitting between 70 and 80mph the full journey. Thats higher than what ive seen previous but believe that to be with the fact it was a lot milder..
 

ernie

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Apr 3, 2006
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554
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Scotland East
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C Class, W205 Sport 2018
I will have a look at what you have said mate.. seems to be sitting ok on the dash but I understand it could be off under the bonnet.. I thought about terra clean but again didn't know anyone who has had it done so that's good to know. I had the car out on a big trip yesterday and averaged 37mpg. 572 miles average speed 55mph so was literally all motorway sitting between 70 and 80mph the full journey. Thats higher than what ive seen previous but believe that to be with the fact it was a lot milder..
In milder weather the MPG should certainly improve and as we move towards Spring, it should improve further as the oil companies revert to the 'Summer Blend' for their diesel.

I've certainly seen some surprisingly low MPGs this winter, but my car has only done 500m since Xmas with an average consumption of well under 40MPG, previously it would have been nearer 50.

Ernie
 

ernie

Active Member
Joined
Apr 3, 2006
Messages
554
Location
Scotland East
Car
C Class, W205 Sport 2018
It is getting up to temperature yes.. and all tyre pressures are correct. I understand its a heavy car, however I know someone else with same car and they seem to still be getting around 10 mpg more than me so really wanted to see if this was across the board.. Sorry the Co? Not following with that?
How about getting the 'someone else' to follow you, both either starting with a cold or hot engine, with the OBCs zeroed and drive a few miles to get a comparison. This won't be entirely accurate, but might help to identify how big the problem is?

Out of interest, are you using MB in Grangemouth or Edinburgh to check it out?

ERnie
 

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