FreeWoRLD

Hey guys,

I had been driving my (new to me) 2018 GLC 300 for the first 5,000 miles or so in "Comfort" mode only. My driving style is extremely boring and smooth. Please don't judge , I don’t care about the gas mileage much, I just like the smooth ride.

Well, for the past few thousand miles, I have completely switched to using "Economy" mode only. As soon as I start the vehicle, I just switch to the "E" mode and have been very happy with it.

However, recently it has gotten my attention that sometimes the "E" mode keeps the rev around 2,000 rpm and decides to keep the current shift, even though I am on a pretty flat road. It just delays upshifting for longer time, then finally does the change.

What is strange is that as soon as I switch to "C" mode right when that happens (when I notice transmission is not upshifting, that I think it could), with the "C" mode the transmission will shift to a higher gear right away. I've even tried to drive on the same road with similar conditions and I do notice "C" mode upshifts sooner than the "E" mode.

I was wondering if you would have any idea why this could be happening? Could it be that the transmission adapts to the driving style over time, so my "C" mode is more economy-like now? And if transmission adapts, then does it only apply to "C" mode?

Sorry if this is a non-sense question but I am just curious. Thanks for anyone to take the time to reply.

superswiss

Each drive mode has its own strategy. Economy mode for example uses Glide mode which decouples the transmission and lets the car glide if you take the foot off the throttle. Comfort mode doesn't use Glide mode, so instead it may decide to upshift sooner in order to have smoother coasting. Hard to tell really, but yes the transmission adapts to your driving style as well and it does that in every mode. Not really sure if it keeps a separate profile for each mode or if it builds an overall profile of your driving style.

edpare

Over my 38k miles, I find E mode gives later upshifts and slower acceleration than C mode. As superswiss said, the big deal is glide mode which lets me “hyper mile” like I used to drive on my Prius. IMHO, Mercedes’ genius is in mapping the tune to use less gasoline even at higher revs.

FreeWoRLD

Some relief knowing that I wasn’t crazy. Looks like some others have noticed the same in the past.


https://mbworld.org/forums/glc-class...ear-70mph.html

wwjdx

How does one RESET this adapt profile on a vehicle bought used? 2022 GLC 300 4matic

superswiss

It varies by model and I'm not sure it's still a DIY with the 9-speed, but in the past it was done via throttle pedal as described at the link below. But as said, I think with the latest transmission it has to be done through XENTRY. To be honest, though, the adaptation is a continuous process. Instead of resetting it, just try driving the way you do for a while. It should adapt. It will also adapt to a temporary change in driving style. For example if you go for a spirited drive, it will likely shift more aggressively after that for a while before it settles down again. At least that happens with my AMG.

https://xentry.mercedes-benz.com/home/

wwjdx

thanks!

W205C43PFL

Though it has a set of adaptations in different drives modes, no?

X253AndBeyond

Yes, I noticed this as well when I took delivery as well almost 3.5 years ago. Like you, I have since always been driving on E mode. I have found that E upshifts later and it also shift smoother than any other mode - or, at least to my experience. I just keep linearly pressing the accelerator until I get up to speed and the shifts are as smooth as can be, and I really appreciate that. I am not able to replicate that seemless shifting behavior in the other drive modes.

W205C43PFL

It is probably smoother because the transmission has more time to think about when to shift. As the throttle is more relaxed and lazy than in even Comfort mode.

FreeWoRLD

For future reference;

Happy to update that the issue is completely gone. (Please see my latest comment below)
Eco mode immediately upshifts to 8th and 9th gear on all conditions now. It would never go above 7th gear, even at highway speeds at around 77-80 mpg recently.

What fixed it was the controversial “transmission reset” procedure. I have always thought that to be nonsensical, however, first hand experience that it fixed the issue that I have been having for a very long time. I have done nothing else but only this so called "transmission reset" procedure, and after completing the steps, I noticed the Eco mode shifting freely to higher gears on my very first drive, even at lower speeds. Surprisingly, got a 34mpg on the same exact commute that I have been always getting 29-30mpg, which I do not care tbh.

So, with my experience and with the vehicle that I have (2018 GLC 300 - 9G tronic), I can confirm that procedure has an effect. Still not entirely sure exactly what that procedure does, but it did whatever it has done to revert back to the original, expected condition. I personally believe it resets the throttle.

The steps of the procedure that worked for me;

• Closed the driver door
• Pushed the start button twice without pressing down the brake pedal (engine does not start by doing that)
• Tuned off AC and the head unit (by pressing the off button on the center console
• Pushed down the gas pedal fully including the kickdown switch and held it for about 3 minutes
• Pushed start button once to turn off the vehicle (Engine was not running) while still pushing down the gas pedal
• Kept pushing down the gas pedal for another 2 mins
• Released the gas pedal and waited in the car until the screen on the dashboard (speedometer) goes off

Did these steps twice, just to make sure not to miss anything

W205C43PFL

Ya it probably just reset the throttle position sensor, glad it worked for you though either way : )

wwjdx

Where did you find this process?

FreeWoRLD

It was mentioned on multiple forums, including mbworld.

ThosHrubecky

Thanks for bringing that to my attention! From YouTube and this forum, I'm building a nice list of "To do..." items once I complete my purchase.

TGH

FreeWoRLD

hope you enjoy your new ride!

FreeWoRLD

The issue has come back. Transmission, when in ECO mode, is back to the original issue (!) which delays upshifting to 8th or 9th gears.

Upon closer observation, I have developed a hypothesis. I do not believe this to be a malfunction; rather, it appears to be an intentional design feature.

It seems that this persistent tendency to remain in 7th gear occurs only during cold starts and continues until approximately 15-20 minutes of driving have elapsed. After this period, the transmission begins to function as expected, shifting into 8th and 9th gears as necessary.

My theory is that in ECO mode, the vehicle purposefully maintains 7th gear, thereby sustaining RPMs at or above 2,000 even during highway driving. This behavior serves the specific purpose of expediting the elevation of engine oil temperatures to their optimal range. It is worth noting that I am referring to oil temperature rather than coolant temperature. Typically, the oil temperature reaches its optimal operating level within 5-10 minutes, following the attainment of the correct coolant temperature, resulting in an overall time frame of approximately 15-20 minutes.

When the engine oil reaches its ideal temperature, it contributes to improved fuel efficiency and offers enhanced protection to the engine. In essence, the oil performs at its best when operating within the specified temperature range, and this appears to be the primary objective.

Perhaps this might be why the vehicle's operating manual recommends utilizing ECO mode during the initial 1,000 miles of driving. If the sole purpose of this recommendation were to keep RPMs low during the break-in period, it raises the question of why the manual also advises driving at varying engine speeds during this same interval.

If my hypothesis proves to be accurate, ECO mode could indeed yield long-term benefits for the engine. This advantage would be particularly evident during shorter trips but could extend to longer ones as well. Additionally, it may contribute to the prevention of LSPI (Low-Speed Pre-Ignition) since cold engines under load and operating at low RPMs are conducive conditions for LSPI to occur. The demands of 8th and 9th gears on the engine should not be underestimated and couple that with cold engine oil, not good.


Conversely, "C" (Comfort) mode does not prioritize these considerations and focuses primarily on providing comfort to the driver. Consequently, it freely upshifts to higher gears. It is important to note that comfort does not equate to high RPMs. I intend to verify whether C mode immediately upshifts without a warm-up period, which aligns with my recollection, but I will confirm this tomorrow morning.

- UPDATE 10/11: Yup, I can confirm Comfort (C) mode does not follow the same behavior. Tried this morning (identical driving conditions, ambient temperature, etc). and the result is that as soon as I got on the highway which was less than 5 mins of total drive time, I was already on 9th gear. So, C mode does not behave the same as E explained above and it does go into higher gears regardless of what the engine oil or coolant temperature is.

Additionally, Here’s another way to look at it;
This might be a "feature", or rather a "fix" added to the transmission firmware later on. Some other posts mention about having this behavior after an update to the transmission. Could it be that Mercedes-Benz realized the piston cracking issue with 2016 models and tried to prevent it with such a firmware update? Here's a post where someone mentions experiencing this behavior only after a software update (post #10). Here's another post (post #5) where the person mentions not having the issue on his past 2016 model, but on his 2017. Guessing his 2016 model was not updated with the new firmware or it was not available, then his 2017 got the update.

It is entirely possible that my assertions are incorrect, and in that event, I invite you to disregard the entirety of my commentary.

edpare

So, after reading your last post, I started my cold 2020 GLC300 RWD and drove 5miles /10 minutes to a highway when I set the cruise to 65 in ECO mode and watched it drop into 9th gear, like always. I like your logic except that you can see 9th gear in C OK, and C downshifts at lower revs than E.

FreeWoRLD

Mine is not 2020, I have the 2018 model and mine does not behave the same as you describe with your 2020 model.

I do also see other posts with earlier year models than 2020 with the same behavior.

I mean we don't even have the same engine - isn't 2020 model on M264 ? If so, we can't expect to experience the same results from both vehicles.

The other post with similar concerns;
https://mbworld.org/forums/glc-class...ear-70mph.html