Hi Guys, I was lucky for my recent purchase of a 4000 mile used C63S Cabriolet ocean blue edition. Since I sold my 2015 C63S sedan in 2018 I missed AMG so much for the past three years!

Now by comparison I notice the gas mileage between the two differs a lot. Even by driving like a grandma I couldn't get anything better than 16~17MPG on my cabriolet. (10 mile trip little city and more highway) I remember on the sedan I was easily getting above 20MPG if drive gently, and about 26MPG purely on high way. I haven't done any long road trip on the cabriolet yet but I doubt it would get better than 20MPG.

Also while the cabriolet is gliding, I notice it slows down much faster than a GLC300 loaner I drove, also under gliding. (Gliding is when the car reaches above certain speed and if throttle is released, the transmission automatically goes to a neutral position and engine runs at 600rpm.) Driving the GLC I feel very little resistance.

Not sure how many of you are cabriolet owners, but I'd love to hear your point of views

Welcome back. Wrong car if you care about mpg, but it does pretty well considering what it is, especially highway mileage. Few cab owners around here. I have a coupe and FWIW my lifetime average over 24k miles is 15.7 mpg, but on a long distance highway trip I can easily get 23-24 mpg average with DISTRONIC engaged and no traffic. The overall average is low, because of around town driving and my lead foot . I do have the FL with the 9-speed transmission, though, so highway mileage is a bit better. I don't do gliding mode, though, so can't help you there. The FL no longer glides in Comfort mode. I suspect the cab is a little worse, being the heaviest variant, and I'm guessing the cloth roof isn't the most aerodynamic part on the car and not sure how much mpg is affected with the roof down. Probably doesn't help.

Thanks for replying. Definitely not about care for mpg, just to make sure if the numbers are reasonable
The GLC300 was a FL version so I notice in comfort mode it does not glide. It however has an ECO mode that enables gliding.
I don't see much difference on mpg with roof down. Maybe the 300+ lb added curbweight and wider tires then. The sedan had all 4 wheels 19'', 245 front and 265 back. The cabriolet has 19'' 255 front and 20'' 285 rear.

Regular MB models don't glide in Comfort mode anyway. That's what they have the ECO mode for, but AMGs don't have an ECO mode so in the past, Glide mode was active in Comfort. However, with the FL, Glide mode is only active in Individual mode with the engine setting set to Reduced or Moderate. Essentially you can configure your own ECO mode if you are so inclined. Wider tires definitely make a difference. They are less aerodynamic and have more friction. Officially the sedan and coupe both have the same mpg rating of 17 city and 26 highway for the facelift, but the cab is rated at 17 city and 25 highway. I believe the PFL is rated at 1 mpg less for highway across the board due to the old 7 speed transmission. 8th and 9th gear are both taller than 7th gear in the old transmission, so effectively the 9 speed has two more overdrive gears for highway cruising which is what gives it the slightly higher highway mpg.

I got only 15-17 when drive aggressive and 20 just cruising on the freeway

Is yours 9-spd?

Thanks for the explaination. I do notice on the FL GLC300 that only when cruising smoothly for a while will it shift to 8th and 9th, while driving in town or shortly on high way will only goes to 7th. However, when 9th gear is in the RPM is incredibly low, almost as low as engine of a CVT transmission

*****One of my friends with a 2019 (I think) Cab definitely gets a bit worse mileage than my 2018 non Cab. I have the 7 speed transmission and get about 17-18 mpg if I drive gently in semi-city traffic. Friends car gets maybe 15 mpg, but he like to drive fast with the top down and the wind blowing through what's left of his hair. Overall I don't think he gets more than 16 ish ever unless he is on the highway, top up, etc... The soft top is definitely not as aero as the regular top on these cars - the .cd is a bit higher on the convertible from what I read in an article somewhere - not that much, but enough to affect mileage a bit. If you really wanna kill your mileage, put one of those Thule box carriers on the roof - I would never do that to my Benz but have on another car and it was easily 5 mpg LESS with that box on the top of the roof - especially noticeable at highway speeds.

Yeah, the C/GLC 300 constantly shift in and out of the higher gears, because that 4-cyl engine is a dog w/o boost. The C63 doesn't do that as much because it has enough torque to stay in the higher gears.

7 speed

Pre FL for me, currently says 15.8mph which is pretty much where it stays mixed city/hwy driving. As mentioned glide mode only works in comfort which I'm never in. Sport till it's warmed up then straight to Ind. (pretty much sport+ wth comfort shocks) If I reset it on the Hwy taking a trip I can get about 21. I drive pretty agressively.

Thank you for the data. Yesterday was my first time driving mostly on highway, about 20miles one way. So by the end of my trip of 40 miles I got 15.7 mpg all on comfort. Considering you only drive under sport/sport+, I think my consumption is a little bit away from normal. I don’t think the ocean blue package adds enough weight to drink so much more fuel…

M177/178 engines have about a 6 to 1 "dynamic ratio" when it comes to fuel mileage. Note that the following numbers are for the 20% larger UK/imperial gallons. I use the RoadTrip app to capture my fuel consumption (and tire swaps, etc.) ... i.e., so the consumption is fairly accurate.

The mileage for my 2016 C63 S ranged from about 5 MPG for the typical 2 fill-ups on a track day to 31.25 MPG on a long highway trip (though more typical was about 28 MPG). I haven't done a long-range highway trip in my 2020 GTR Pro, but on my 1 (thus far) full track day it got slightly less than 3 MPG (!!!) and, if I'm behaving myself (OK, once), it seems to be about 17.5 MPG with mixed city/highway driving and about 14 MPG if I take a few people for a demo ride between fills.

The point is that, with an AMG V8 (and likely any AMG engine ... it's also true with my C43) you will experience widely differing fuel mileage depending upon how the vehicle is being driven. Drive it smoothly and gently and it can get pretty respectable mileage, considering it's a high-horsepower engine. Drive it "like you stole it" and you will get less than 20% of that fuel mileage. Isn't computer-control wonderful?!

******I drove about 100 miles today in my car (C63s), mostly highway and got about 25mpg. I was in comfort mode and very gentle on the gas, cuz that's how I sail.

Yeah unless you were in the triple digits the whole trip that is pretty bad.

According to the mmc app I got 9.2L/100km last night on a 90km drive home averaging 80km/h. Highway driving in sport+ with occasional full throttle but no kickdown to overtake turtles. FL sedan btw. Couldn't care less about my mileage unless its alarmingly low.

As many others have said, if you care about MPG any AMG or Mercedes in general for that matter, is not the car for you. An AMG is supposed to be about performance, MPG be damned.

2021 Post-FL Cab C63S owner here and we can average around 20 on the highway doing the limit +5. I've noticed that I can pull a slightly higher average if I drive the limit, but who drives the limit in an AMG?

I assume your 2016 C63 S is a coupe? 28MPG is pretty good. If I switch my odometer screen to the dynamic consumption, while driving on flat high way I see the bar stays at about 20MPG. That's 40% more consumption than that of a sedan/coupe!
If the 6 to 1 applies to the cabriolet, it'll hit 3MPG on track lol.

Not driving the limit for sure Only because I just bought the car and want to make sure everything is working correctly. If the gas mileage is too bad even if driving gently, it could be an indication that something is not right.

Looks like the 9-spd really helps to save fuel. I get very similar mileage on the 2015 C63s sedan but in comfort mode.

Sounds about the right MPG for sailing

Thanks for the data. I'll try next time reset it on high way and see if I get better than 20.