Bad fuel economy
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GLC 300 4matic
Bad fuel economy
Hello,
I just got a 2020 GLC 300 4Matic. I went on a 300 mile trip on comfort mode and cruise control at 75mph and only got 22mpg.
I was wondering if anyone has advice to maximize my fuel efficiency. I know I should’ve been on ECO mode. Is it better to drive manually (without cruise control) in order to benefit from the cylinder deactivation? It doesn’t seem like cylinder deactivation kicks in when cruise control is active.
Appreciate the advice in advance.
Thank you,
Idan Tal
I just got a 2020 GLC 300 4Matic. I went on a 300 mile trip on comfort mode and cruise control at 75mph and only got 22mpg.
I was wondering if anyone has advice to maximize my fuel efficiency. I know I should’ve been on ECO mode. Is it better to drive manually (without cruise control) in order to benefit from the cylinder deactivation? It doesn’t seem like cylinder deactivation kicks in when cruise control is active.
Appreciate the advice in advance.
Thank you,
Idan Tal
Out Of Control!!
Joined: Nov 2018
Posts: 11,403
Likes: 5,325
From: San Francisco Bay Area
2019 C63CS
What kind of fuel economy were you expecting? 22-23mpg is the average for these boxy things according to fuelly. The speed is part of your problem. Drag grows exponentially with speed. Going 75 mph instead of 65 mph increases drag by ~30% while speed is only 15% faster. Going 75 mph instead of 55 mph has 85% more drag, so almost double the wind resistance going only 20 mph faster and SUVs are not exactly aerodynamic. Slow down if you want better fuel economy.
https://www.fuelly.com/car/mercedes-benz/glc300
https://www.fuelly.com/car/mercedes-benz/glc300
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Joined: Mar 2016
Posts: 1,040
Likes: 161
From: Melbourne, Australia
2016 GLC 250d AMG pack, 2017 GLC Coupe 250d AMG pack , 2002 BMW 330Ci convertible, 2021 BMX X1 sD20i
How many miles are on the speedo ? Has the car been serviced annually to MB specs ?
A few things to do before paying the Dealer to run a set of test >
firstly prior advice here re speed is excellent.
1. Check tire pressures as per fuel filler door for front and rear, at load and ‘high speed’. These are cold psi, not psi after you have driven to fuel station to add air. You could have a garage ‘empty’ the air in your tires and refill with Nitrogen, larger air particle, less heat build up and less loss of air between checks, usually used in race track, but having 2.5 Ton rearing down the highway at 75mph will add heat and stress to the rubber.
2. Increase PSI to about 4PSI higher to give better handling, better braking response and better mileage, some slight decrease in comfort, but worth it.
3. Add an after market bottle of fuel tank and fuel injector cleaner, try a heavy duty one from a reputable shop. May have to repeat with new bottle after 3 or 4 full normal refills. Also what grade of fuel ?, try non eco fuel, use highest Octane, better engine response and fuel usually had additives in fuel to clean your system.
4 after your next oil change, add a bottle of friction modifier, like a ceramic or teflon coating in the engine with all moving parts, helps reduce friction and heat, engine functions better.
5. Certainly try Eco setting next time, then run manual changes, BUT Adaptive cruise control is worth it, less fatigue, less speeding fines and a better experience.
Let us know how you go.
A few things to do before paying the Dealer to run a set of test >
firstly prior advice here re speed is excellent.
1. Check tire pressures as per fuel filler door for front and rear, at load and ‘high speed’. These are cold psi, not psi after you have driven to fuel station to add air. You could have a garage ‘empty’ the air in your tires and refill with Nitrogen, larger air particle, less heat build up and less loss of air between checks, usually used in race track, but having 2.5 Ton rearing down the highway at 75mph will add heat and stress to the rubber.
2. Increase PSI to about 4PSI higher to give better handling, better braking response and better mileage, some slight decrease in comfort, but worth it.
3. Add an after market bottle of fuel tank and fuel injector cleaner, try a heavy duty one from a reputable shop. May have to repeat with new bottle after 3 or 4 full normal refills. Also what grade of fuel ?, try non eco fuel, use highest Octane, better engine response and fuel usually had additives in fuel to clean your system.
4 after your next oil change, add a bottle of friction modifier, like a ceramic or teflon coating in the engine with all moving parts, helps reduce friction and heat, engine functions better.
5. Certainly try Eco setting next time, then run manual changes, BUT Adaptive cruise control is worth it, less fatigue, less speeding fines and a better experience.
Let us know how you go.
MBWorld Fanatic!
Joined: Feb 2004
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From: Milton/Westport, MA USA
me: 2015 SL400 & 2015 ML400; wife: 2022 GLC Coupe; daughter: 2017 GLC SUV
while the particulars are rife with differences this reminds me a lot of my CLK experience. 22mpg was about all I ever got in my CLK350, and 75mph highway drives were the bulk of my miles. When I had to unexpectedly replace that car due to an engine issue I reluctantly bought a 550, the only CLK available to me at the time. That engine handled 75mph so effortlessly I routinely got 28-29mpg and sometimes got 30mpg or more. It's why I chose an ML400 over a 350. My wife gets about 22mpg in the GLC on average with mixed city/highway driving in ECO.
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Member
Joined: Dec 2014
Posts: 179
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From: Arizona
2020 GLC300 touring version (but I miss my '93 300SE W140 tank)
30.6 mpg
2020 GLC300 RWD CPO, 31k miles since purchase, 30.6 mpg lifetime average. 50% I road @75mph, Driver Assist on always, ECO mode always, Auto start/stop always, adaptive cruise control when not gliding, system disengaged when downhill is steep enough to "Glide". Michelin Defenders @ 34psi. Name brand premium gas always. M-B service: two A's, one B. Best mileage above 8,000 feet in Colorado.
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Out Of Control!!
Joined: Nov 2018
Posts: 11,403
Likes: 5,325
From: San Francisco Bay Area
2019 C63CS
while the particulars are rife with differences this reminds me a lot of my CLK experience. 22mpg was about all I ever got in my CLK350, and 75mph highway drives were the bulk of my miles. When I had to unexpectedly replace that car due to an engine issue I reluctantly bought a 550, the only CLK available to me at the time. That engine handled 75mph so effortlessly I routinely got 28-29mpg and sometimes got 30mpg or more. It's why I chose an ML400 over a 350. My wife gets about 22mpg in the GLC on average with mixed city/highway driving in ECO.
Last edited by superswiss; Apr 15, 2023 at 12:29 PM.
MBWorld Fanatic!
Joined: Oct 2009
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From: Colorado
'21 AMG53 wDPP & ARC, 19 GLC300 - Former-03 C240,2 ML BlueTecs,20 GLE450 E-ABC,15 Cayenne D,17 Macan
In order to "average" 70 requires mostly 80+ driving, so our trips "average" 60mph / 30 - 32mpg. It still involves some aggressive driving and a radar detector.
Aero does impact the mpg, since averaging 50mpg gets us 32ish.
Interestingly, our '20 GLE450 3.0 six got +2 highway and -2 city.
I believe I get better mileage with My Foot than with Distronic because I can anticipate things like traffic and hills. But I like my Distronic.
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Joined: Feb 2023
Posts: 59
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GLC300, C300
I just did a 200 mile trip last weekend. 2020 GLC300 4matic 27k miles. Pulled 29.4 mpg in the rain and using ac on roads that varied in speed limit from 45 to 70, with me observing legal limit and using cruise control where practical. I only fill up with 93 octane fuel from TopTier stations.
Member
Joined: Apr 2014
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18 GLC300 4M
Idan Tal,
My 2018 glc300 4 matic, 40 lbs tire pressure , always gets around, and above 30 mpg on nonstop highway trips driving at 65-75 mph, around 22 in city and averaged 22 mpg over the last 40K, I always stay in Comfort mode above 60mph. Unless you are driving long uphill pulls and/or driving aggressively you should be getting better than 22.
you must still be under warranty. Have your dealer test drive the vehicle.
My 2018 glc300 4 matic, 40 lbs tire pressure , always gets around, and above 30 mpg on nonstop highway trips driving at 65-75 mph, around 22 in city and averaged 22 mpg over the last 40K, I always stay in Comfort mode above 60mph. Unless you are driving long uphill pulls and/or driving aggressively you should be getting better than 22.
you must still be under warranty. Have your dealer test drive the vehicle.
