Daily Eco drive what setting ?

SquabzZz

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Hey people this being my first merc I still have a bunch of questions to ask!!

For everyday economical driving what setting should I have the merc in Comfort or Sport ?

I know the gear changes depend on how your foot is on the throttle but still what setting should I be in ?
 
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paul hayward

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Hey people this being my first merc I still have a bunch of questions to ask!!

For everyday economical driving what setting should I have the merc in Comfort or Sport ?

I know the gear changes depend on how your foot is on the throttle but still what setting should I be in ?

comfort and a very gentle right foot will help the MPG ...No fun though;)
 

whitenemesis

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I have never seen any mpg advantage in either of the settings.

Save the C for when the going gets slippery and enjoy the S for day to day driving.

If you want economy, easy on the right foot...
 

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Most of use find little difference, C should be the best one for in town work as it is a second gear start
 
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SquabzZz

SquabzZz

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Most of use find little difference, C should be the best one for in town work as it is a second gear start


Sport it is ! Been driving around in comfort all the time lol
 

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I always drive in C; S is too frenetic. C does not mean second-gear starts in every car: mine never starts in second.

You'll see far more significant fuel savings from driving style: looking ahead and avoiding unnecessary changes of speed. Even a perfectly aerodynamic frictionless car will use energy accelerating and deceleration: kinetic energy is ½mv², and that energy comes from fuel and disappears as brake heat (and other heat losses). It matters little where teh shift points are.

Curiously, it doesn't matter how hard you accelerate either, if you're going to then maintain the speed for a long time (such as on a motorway slip road): the car uses the same energy to get from speed 1 to faster speed 2 whether you spread it out over a long time or give it the beans — provided you don't use wide-open throttle and end up over-fuelling.
 
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Naraic

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I always drive in C; S is too frenetic. C does not mean second-gear starts in every car: mine never starts in second.

You'll see far more significant fuel savings from driving style: looking ahead and avoiding unnecessary changes of speed. Even a perfectly aerodynamic frictionless car will use energy accelerating and deceleration: kinetic energy is ½mv², and that energy comes from fuel and disappears as brake heat (and other heat losses). It matters little where teh shift points are.

Curiously, it doesn't matter how hard you accelerate either, if you're going to then maintain the speed for a long time (such as on a motorway slip road): the car uses the same energy to get from speed 1 to faster speed 2 whether you spread it out over a long time or give it the beans — provided you don't use wide-open throttle and end up over-fuelling.

Interesting. How does a car use energy on deceleration? Especially MB...since with the gearbox engaged and foot off the accelerator...fuel is cut off above a certain road speed?
 

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Interesting. How does a car use energy on deceleration? Especially MB...since with the gearbox engaged and foot off the accelerator...fuel is cut off above a certain road speed?

Sorry, poor phrasing on my part. Accelerating, you are converting expensive chemical energy to transient kinetic energy. You then lose it decelerating (converting kinetic energy to heat through friction, whether road, brake or air). Of course, you also expend chemical energy overcoming friction and other losses to maintain a steady speed or to keep the engine turning over at rest.
 
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the car uses the same energy to get from speed 1 to faster speed 2 whether you spread it out over a long time or give it the beans — provided you don't use wide-open throttle and end up over-fuelling.

Although, I have also heard a theory that wide open throttle has less drag against the throttle plate and so is the most efficient use of it, so to accelerate up to a speed you should use open throttle to get there, release and basically keep using open throttle/release(loose speed) open throttle... etc to drive along, as driving with partial throttle is innefficient. No idea what truth there could be to that, plus even if it was, thats a horrible way to have to drive!
 

Troon

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Although, I have also heard a theory that wide open throttle has less drag against the throttle plate and so is the most efficient use of it, so to accelerate up to a speed you should use open throttle to get there, release and basically keep using open throttle/release(loose speed) open throttle... etc to drive along, as driving with partial throttle is innefficient. No idea what truth there could be to that, plus even if it was, thats a horrible way to have to drive!

In a simple engine, WOT or close to it is most thermodynamically efficient: look up "brake specific fuel consumption charts" which are contour maps showing the grammes of fuel needed to produce 1 kWh of energy, plotted against rpm and load. Typical engines are most efficient around the peak torque speed at about 80% load.

Modern ECUs tend to overfuel at WOT and close to it, to improve performance and cooling at the expense of efficiency.

So yes, "burning and coasting" is an efficient way to drive if you're in a fuel economy challenge vehicle, like the 8000mpg ones that physically shut off the engine and roll during the coast phase. In a real car, though, other losses would make this much less beneficial and as you say, it's a horrible way to drive.

The other problem is that modern cars are so over-powered, you can't stay at 80% load for long without losing your licence. This is why range-extended electric vehicles use a small engine, to be able to run it at its optimum point to charge the batteries for minimum fuel expenditure.

It's a complex subject with diminishing returns. The two key points I practice when driving are:
  • avoid braking as much as possible by looking ahead and anticipating variations in traffic speed, minimizing my own speed changes;
  • remember that wind drag goes up with the square of the speed and that this drag dominates other forces at high speeds: driving at 60 or 70 is much more efficient than at 80 or 90, putting aside the legal aspects.
 

orb the Impaler

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It's a complex subject with diminishing returns. The two key points I practice when driving are:
  • avoid braking as much as possible by looking ahead and anticipating variations in traffic speed, minimizing my own speed changes;
  • remember that wind drag goes up with the square of the speed and that this drag dominates other forces at high speeds: driving at 60 or 70 is much more efficient than at 80 or 90, putting aside the legal aspects.

The latter has an amazing difference on my commute to Leeds (M62) every day.

If I drive in in heavy traffic with quite a bit of stop-start at the Leeds end I get over 63mpg from my SLK.

Do the same trip at an earlier time and hence spend a lot of time at around 85 this drops to low 50s and as far down as 45mpg. An amazing difference.
 

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Although, I have also heard a theory that wide open throttle has less drag against the throttle plate and so is the most efficient use of it, so to accelerate up to a speed you should use open throttle to get there, release and basically keep using open throttle/release(loose speed) open throttle... etc to drive along, as driving with partial throttle is innefficient. No idea what truth there could be to that, plus even if it was, thats a horrible way to have to drive!

In Sweden all economy test and runs are done by getting the car into a higher gear as soon as possible, then back off, they do it the same way in Germany, so you are correct from a practical point
 
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SquabzZz

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Wow lots of good information but that's not really what I meant oooops

Just really ment when I'm driving to get as many mpg as possible would it be better in comfort or sport mode but I guess it don't really matter just need careful driving with forward looking
 

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Anticipation is the best form of economy setting.
 

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Do you have the 7g box or the 5 speed
 

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It's a 5 speed auto (don't think it's a 6 speed)

Has the paddle shift too :cool:

If the 722.6 5 speed box, in town use the C it should be marginally better, it will not roll back on hills as well
 
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SquabzZz

SquabzZz

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If the 722.6 5 speed box, in town use the C it should be marginally better, it will not roll back on hills as well

Need to actually look into the box as Parkers state there a 5 speed and the HpI I did on the car states its a 6 speed auto lol

Regardless I love the car
 

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5 or 7 not 6 :D:D
 


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