Though not a primary concern, does anyone have some real world experience on highway mileage for the C300 and C400? it see, some cars do better than listed; my daily driver Acura TSX is listed as 29 mpg highway and I get 30 mpg overall rural driving. My wife's Infiniti doesn't get close to the listed mileage.

 

I do not own a C class but I do drive an EVO X daily. About 12 miles of hwy each way everyday. I get around 23mpg tops. My co worker with a CLA250 gets around 27 I think. Our shop CLA45 sits in R&D most of the time and doesn't get a lot of action yet.

 

My C400 with 500 miles got 28 mpg (according to the trip computer) on a 110 mile trip (each way) to New York City and back last weekend. This was all highway driving.

 

does anybody know how big a difference driving in eco mode actually makes? also what about auto start/stop?

 

Doesn't make much difference between Eco and comfort from what I can tell so far, but I've only drive about 500 miles so far and taken it easy on the pedal so far. The start/stop I'm still getting used to, doubt again it's much difference tough.

 

what about sport+? does that burn fuel much much faster?

 

100% it will! I tried sports+ briefly and it felt great.
Still going through the break in period, but the pedal response is much better than in Eco/Comfort as expected, it's night and day.
Can't wait to floor it...

 

My trip back from the dealer was a two hour drive at 60 - 78 mph ... mostly highway until I got close to home. There were several long hilly stretches, so it wasn't really a level run at all. I was surprised that when I pulled into my driveway the car's computer showed 29.4 mpg. Now, with two weeks of all local driving, with lots of hills, I'm showing an average after reset of 27 mpg. Those are really strong figures, especially for a brand new car.

I'm used to a car's trip computer being as much as 10% optimistic on the fuel economy readings. I did check one tank manually, and was surprised to find the car's computer was within .3 mpg of the actual numbers. I didn't expect that.

 

UK owner of C220 diesel auto. Still breaking in but a 200 mile trip on highways and twisty country roads showed 54.3mpg. So far so good.

 

After 1200km I am averaging 10.9l/100km which works out to be 21.58mpg(US)
On my W204 I averaged 13.7l/100km after 45,000km (17.17mpg(US)).
I don't usually watch fuel economy but I am surprised at this improvement. I will keep an eye on it to see if its maintained.

 

I have 1100 miles on my C300 and I do mixed city and highway (stop and go highway) and I'm very pleased with my 29.7 MPG that said I leave it on "Comfort mode" most of the time. I went from a 2010 6cyl 220hp BMW getting 24.5 mpg to this and I never thought I would say I'm loving a 4cyl engine but I am. It may sound like crap but it goes.

 

Same here. Coming off a big 6 cylinder Volvo S60 R-Design, my C300 is averaging well over 27 mpg with mostly local driving in mountainous terrain. That's a solid 6 mpg better than the Volvo. That's even better than my 2009 Audi A4 2.0T.

I opted for the C300 for the better gas mileage, even though I was a bit reluctant to pass on the power of the C400. So far, for me anyway, it seems like a pretty good trade-off.

 

I got 28 mpg in my C400 doing all highway, when i do mix of city since i live in one and highway I get around 23, i would say most of it city though.

 

Impressive, I guess you were very judicious with the throttle!
Turbo engines can give good economy under light load conditions, but once you spool up those turbos, fuel economy suffers significantly.

 

The 300 is more than fast enough. It just has to be wrung out more for "spirited" driving. Some would consider that more "sporting" anyway. That's the model I tested, on sport plus it felt plenty strong, on comfort it has plenty of power for everyday duty.
Ill let you know when I get my car Ill let you know what the 400 is all about.

 

Most new FE computers are right on the money. You have direct injection to thank for that, the flow rate measurements are very precise.

 

To be honest on my trip I got 28 miles a gallon I was gunning it many times. I feel like if I drove ideally situated on a long trip I could get 29 or 30

 

Better yet!

 

200kms in and 3/4 local 1/4 highway. avg 11.7l (20mpg) for my C400.

 

YES!!!

 

From what I have read S/S is worth about an extra 1 mpg in city driving.

Get used to it because it will be on all cars soon. Mfgs need every help they can get to meet EPA mandates.

 

Do you calculate exact figures or is it based on the car computer? My computer shows 8% less than actual figures.

 

Can't beat actual.

 

mpg on dash is not accurate...
use fuelly or similar to track mpg after each fillup...

 

There is no such thing as real world MPG since real MPG has a myriad of confounding factors. If you go to a Prius sounding board you would think that Priuses average 70mpg Take it on faith the 400 is a mid 20's car and the 300 is a high 20's one, on average. As long as you keep the boost low your MPGs will be quite good, once you get those turbos spooled up economy will suffer. Its simple physics, the whole idea for any boosted engine is to get more air (and GAS) per stroke into the cylinder!