GLC300 High Fuel Consumption
Thread Starter
Senior Member
Joined: Jul 2014
Posts: 305
Likes: 22
From: BC
G11 750i Individual, X166 GL550 Designo, W222 S550e, W221 S63
GLC300 High Fuel Consumption
I got a 2022 GLC300 as a loaner vehicle and was surprised about the fuel economy I'm getting; for truly stop and go traffic in town with traffic lights, I'm getting around 17.5 l/100km which is basically 13.5 mpg in both eco mode and with auto start stop enabled. On city drives with some slightly longer stretches without stop signs and traffic lights where I can coast, I'm still only getting 13.5 l/100km, around 17.5 mpg which still is pretty horrid considering the displacement
The 'from reset' figure on the vehicle shows as 10.5 l/100km, around 22.5 mpg which I can't seem to achieve. I'm also driving with a pretty light foot and not even spiritedly; when I was in sport/sport+ and driving in a more spirited manner yesterday, it was in the 19/20 l/100km or 12 mpg figure.
How do people manage to get decently high mpg on their i4 vehicles or are these more suited for longer distance, highway drives?
For reference, my S63 gets around 22 l/100km in the city whereas the diesel GLE gets around 11.5 l/100km also in the city, both on the same route driven as the GLC today
The 'from reset' figure on the vehicle shows as 10.5 l/100km, around 22.5 mpg which I can't seem to achieve. I'm also driving with a pretty light foot and not even spiritedly; when I was in sport/sport+ and driving in a more spirited manner yesterday, it was in the 19/20 l/100km or 12 mpg figure.
How do people manage to get decently high mpg on their i4 vehicles or are these more suited for longer distance, highway drives?
For reference, my S63 gets around 22 l/100km in the city whereas the diesel GLE gets around 11.5 l/100km also in the city, both on the same route driven as the GLC today
Out Of Control!!
Joined: Nov 2018
Posts: 11,455
Likes: 5,353
From: San Francisco Bay Area
2019 C63CS
Stay out of boost. The dirty secret of small displacement turbo engines is that the fuel economy goes to the crapper the moment boost kicks in Problem is w/o boost these engines are dogs. The longer you stay out of boost, the better the fuel economy, so yes long highway cruising does wonders, or driving it like a grandma.
Thread Starter
Senior Member
Joined: Jul 2014
Posts: 305
Likes: 22
From: BC
G11 750i Individual, X166 GL550 Designo, W222 S550e, W221 S63
Stay out of boost. The dirty secret of small displacement turbo engines is that the fuel economy goes to the crapper the moment boost kicks in Problem is w/o boost these engines are dogs. The longer you stay out of boost, the better the fuel economy, so yes long highway cruising does wonders, or driving it like a grandma.
That's also interesting since both my vehicles also have turbos.
Is it because the 63 a lot more power and the diesel, more torque than the i4 so the turbos build up less pressure for the power/torque needed to move the vehicle from a standstill typical city driving?
Out Of Control!!
Joined: Nov 2018
Posts: 11,455
Likes: 5,353
From: San Francisco Bay Area
2019 C63CS
Thanks for the info.
That's also interesting since both my vehicles also have turbos.
Is it because the 63 a lot more power and the diesel, more torque than the i4 so the turbos build up less pressure for the power/torque needed to move the vehicle from a standstill typical city driving?
That's also interesting since both my vehicles also have turbos.
Is it because the 63 a lot more power and the diesel, more torque than the i4 so the turbos build up less pressure for the power/torque needed to move the vehicle from a standstill typical city driving?
Last edited by superswiss; Oct 26, 2022 at 10:40 AM.
Member
Joined: Dec 2014
Posts: 179
Likes: 29
From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
Our 2020 GLC300 has 22,500 miles with a lifetime 30.5 mpg in rural settings only. I drive as you describe, staying at or under the speed limit, but I use Driver Assist in ECO mode as much as possible thus letting the car’s computer do the driving. The exception is when passing where, because I hate to be behind anyone, I frequently “do the ton” over 100 mph. I also do mostly interstate driving where I get 27 mpg at best.
Yes, I sound ridiculously optimistic, but it is true. There’s always an outlier, right?
I live at elevations between 4400 and 8200 feet. At 8200 feet I often get over 37mpg. Counterintuitive, but the car uses the turbo more at high elevations. This must have something to do with it.
Yes, I sound ridiculously optimistic, but it is true. There’s always an outlier, right?
I live at elevations between 4400 and 8200 feet. At 8200 feet I often get over 37mpg. Counterintuitive, but the car uses the turbo more at high elevations. This must have something to do with it.
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Joined: Oct 2009
Posts: 7,016
Likes: 2,198
From: Colorado
'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
I got a 2022 GLC300 as a loaner vehicle and was surprised about the fuel economy I'm getting; for truly stop and go traffic in town with traffic lights, I'm getting around 17.5 l/100km which is basically 13.5 mpg in both eco mode and with auto start stop enabled. On city drives with some slightly longer stretches without stop signs and traffic lights where I can coast, I'm still only getting 13.5 l/100km, around 17.5 mpg which still is pretty horrid considering the displacement,...........
There's a good chance that the previous driver filled with the lowest quality gas available.
If you're trying to compare your economy and performance, you really need to run your tank way down and refill with good fuel, before you can make a valid comparison.
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Senior Member
Joined: Apr 2006
Posts: 378
Likes: 15
From: Boston and SWFlorida
2025 GLC300 white, 2023 Taycan RWD black
I just traded a '19 for a '22. My gas mileage is horrible. I fill the tank and my predicted range is 300 miles. I know it has to learn my driving, in the meantime I've put it on E and will see if that makes a difference.
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