2015 C Class C220 Bluetec AMG Line 2.2 - MPG Question

[dubsR33]

Im looking to buy this car:

Mercedes-Benz C Class C250 BLUETEC AMG LINE PREMIUM 2.2 5dr

Now my reservations are that as it has a smaller sized engine, will i be able to achieve similar or better MPG at higher speeds then my current car?

The 2015 C Class C220 CDI Estate has 7 gears exactly the same as my CLK 320 CDI.

So surly traveling at say 90 the whole way, would result in the car being driven at higher revs therefore use more fuel?

If anyone has this car please could you let me know your stats and figures please id very much appreciate it.

Cheers thanks

 

[CaptainChaos]

It's only got four cylinders to fill though!

 

[geraldrobins]

The revs at 90 will be approximately, 2200 so how does that compare with your current car.
But the revs aren't the only thing affecting mpg. The 220 will be more economical for sure. Look at the data.
And how often can you realistically drive at 90 on uk roads anyway.

 

[dubsR33]

The revs at 90 will be approximately, 2200 so how does that compare with your current car.
But the revs aren't the only thing affecting mpg. The 220 will be more economical for sure. Look at the data.
And how often can you realistically drive at 90 on uk roads anyway.

i work early's and i travel 40 miles each way 5days a week, i leave my house at 5am and it takes 40 mins of solid M4 driving to get to work, so my cruise control sits at 90 the whole way everyday. Even the police that i see occasionally who are sat on the side of the motorway don't bother with you for some reason... so realistically its every day.

 

[dubsR33]

i would just like to know what someone with this car/engine gets fuel wise on a tank to tank driving approximately 80ish + mph and mainly motorway driving etc

 

[geraldrobins]

My c200cdi indicates 55-60 mpg on a long run with the cruise set at 80.
Something wrong with your maths as well. 40 minutes at 90 is 60 miles!!

 

[Andyfkettle]

Getting 36mpg on mine but that’s from the wife tootling round to the shops and back and me giving it an odd blast down the Duel carriage way. Not given it a good long steady run yet!

 

[dubsR33]

My c200cdi indicates 55-60 mpg on a long run with the cruise set at 80.

Exactly the sort of information i needed thanks

Something wrong with your maths as well. 40 minutes at 90 is 60 miles!!

So i forgot to write "about" 40 minutes then.. Obviously i don't drive at 90 the moment i leave my house in the small residential roads etc.
Thats when i get on the actual motorway.

 

[GeeJayW]

Get about 47-50 mpg out of our 2016 AMG Line C250d 7-spd auto on a long run with a steady 80 on the speedo (77 by gps) on the motorway sections. It's averaging 43 mpg so far overall.

Daughter has a 2017 Sport C220d 9-spd auto and gets nearly 60 mpg.

 

[dubsR33]

Get about 47-50 mpg out of our C250d 7-spd auto on a long run with a steady 80 on the speedo (77 by gps) on the motorway sections. Daughter has a 220d 9-spd auto and gets nearly 60 mpg.

thanks for your reply chap thats really helpful cheers

Looks like i'll be going for it then..

 

[garycat]

My C220 (170bhp) has hit 68mpg on long motorway runs but that is at 75-80mph. It is not the bluetec version but I believe its mostly the same, just without an adblue tank. (edit - oh and the C250 has an extra turbo?)

However since I changed the wheels to a much larger and heavier sports style wheel, MPG has dropped to about 58-60.

 

[GeeJayW]

thanks for your reply chap thats really helpful cheers

Looks like i'll be going for it then..

No worries, glad to help. Looks like the car you linked has real leather seats rather than Artico, which is a bit of a bonus. It also has Artico dash covering which I think is a nice touch too.

It also has 18" rims, so you might get slightly better mpg than ours.

Enjoy!

 

[Mactech]

I've had a fair number of 6cyl and 4cyl diesel Mercs over the past decade and can confirm that if economy is a priority, then the 4cyl cars are the best bet. My experience says about 20% better. That's like not paying Vat on your fuel bills
Whilst you flag up gear ratios as a concern (5 vs 7 vs 9), and it does make a difference, this is not where the fundamental difference is.

It is in boring old physics!

Internal friction in the 6cyl engine will always be higher that a 4cyl....but the of bigger concern should be the thermal mass of the drivetrain.
Although you engine temp may read normal after 5 or 10 minutes of your 40 minute commute, in reality it will be at least 20 mins before the whole drivetrain (gearbox, axles, corners etc) will be most efficient.
Going from ambient to 90 degree for drivetrain uses about the same energy as boiling 100 kettles
It is little wonder that the mpg from cold starts is relatively poor!
Then you will heat the carpark until it's time to return home.
The 6 cyl engine gets the double whammy of having more 'sticky' parts during the warmup phase and that it has typically 30% more mass to heat up.

Manufacturer's official figures also indicate the approx 20% better fuel economy of the 4cyls, although those tests are all with pre heated cars and one of the reasons very few get close to them in 'real world' driving.

Of course, the 'six' is a smoother and more powerful engine but there is a price to pay.
The very latest 'fours' are getting more refined (and more efficient) with every development step.

 

[geraldrobins]

My C220 (170bhp) has hit 68mpg on long motorway runs but that is at 75-80mph. It is not the bluetec version but I believe its mostly the same, just without an adblue tank. (edit - oh and the C250 has an extra turbo?)

However since I changed the wheels to a much larger and heavier sports style wheel, MPG has dropped to about 58-60.

The w204 c220 is also twin turbo I understand.

 

[garycat]

The w204 c220 is also twin turbo I understand.

Oh really? I thought the difference was that the 170bhp C220 was single, and the 201bhp C250 was twin, or perhaps it is just a different map.

 

[dubsR33]

I've had a fair number of 6cyl and 4cyl diesel Mercs over the past decade and can confirm that if economy is a priority, then the 4cyl cars are the best bet. My experience says about 20% better. That's like not paying Vat on your fuel bills
Whilst you flag up gear ratios as a concern (5 vs 7 vs 9), and it does make a difference, this is not where the fundamental difference is.

It is in boring old physics!

Internal friction in the 6cyl engine will always be higher that a 4cyl....but the of bigger concern should be the thermal mass of the drivetrain.
Although you engine temp may read normal after 5 or 10 minutes of your 40 minute commute, in reality it will be at least 20 mins before the whole drivetrain (gearbox, axles, corners etc) will be most efficient.
Going from ambient to 90 degree for drivetrain uses about the same energy as boiling 100 kettles
It is little wonder that the mpg from cold starts is relatively poor!
Then you will heat the carpark until it's time to return home.
The 6 cyl engine gets the double whammy of having more 'sticky' parts during the warmup phase and that it has typically 30% more mass to heat up.

Manufacturer's official figures also indicate the approx 20% better fuel economy of the 4cyls, although those tests are all with pre heated cars and one of the reasons very few get close to them in 'real world' driving.

Of course, the 'six' is a smoother and more powerful engine but there is a price to pay.
The very latest 'fours' are getting more refined (and more efficient) with every development step.

incredible information, insanely helpful. Very much appreciated thanks

 

[Thrash]

From my experience with a C220d Bluetec, it gets about 60 with cc set at 80. If you're happy to sit below 70 you can easily get nearly 70mpg out of one. Which is a bit annoying cus thats better than my previous 180d and current 200d!

 

[markjay]

I didn't quite get the relation between the number of cylinders, speed, and engine revs.

The engine rev at a given speed is a simple product of the gear ratio and the final drive (diff) ratio. The number of cylinders does not come into it.

The difference between a 4-cyl engine and a 6-cyl engine, is that the 4-cyl engine is likely to produce less torque, meaning it might use a lower gear when cruising at the same speed that a 6-cyl engine would with higher gear. This will result in higher engine revs for the 4-cyl engine.

So when accelerating and in varying driving conditions, the less torquey engine will likely use lower gears overall and shift-up at higher engine revs.

But when cruising at motorway speeds, and transmission will be using the highest gear (overdrive) anyway and therefore engine revs will be the same for the 4-cyl and 6-cyl engines.

What will affect this are (a) different size wheels, and (b) different gear ratios in the transmission box and/or final drive, and (c) different TCU software.

So for lower revs you need the more torquey engine of the two, a transmission box with lower ratios, a TCU mapped for quicker changes at low revs, and bigger-diameter wheels.

But ultimately, if the overdrive ratio is the same, and the final drive ratio is the same, and the wheels are the same size... then when cruising on the motorway the engine revs will be the same for a 4-cyl engine and 6--cyl engine.

The way larger engines can negate some of their higher fuel consumption is by having the TCU mapped for eralier gear upshifts i.e. at lower engine revs, relying on the engine's higher torque.

But even so - some modern 4-cyl engines are more efficient and actually torquier than 6-cyl engines of old.....

 

[garycat]

Oh really? I thought the difference was that the 170bhp C220 was single, and the 201bhp C250 was twin, or perhaps it is just a different map.

(replying to self) OK, just checked on MB website and both 220 & 250 are twin turbo

https://www.mercedes-benz.co.uk/con...c-class/c205/advice_sales/technical_data.html