daannnnggggg. i think my average is like 22mpg.. but i drive the 2.5L lol

 

That looks like my wifes GLK average.

 

Karo this comes from our conversation. My average is 28.1 now that I've driven reasonably. The M271 is so much more efficient than both 2.5 and 3.5 M272 engines.

 

its missing 2 cylinders so your cheating I avg 22.5 usually.

 

Same engine, different result:

 

Not bad

 

I wish it was 50 degrees out. My car has been sitting in my garage all winter.

 

i do to it has not been that warm in way to long lol. Tomorrow i plan on driving as hard as i can to see how bad i can get the fuel millage to be

 

Its a easy 15.. but got 13 before...

 

Cheater, cheater peter eater. You post back your result after at least 250 miles.

 

 

no picture, but my average is around 13

 

pretty heavy

i would be happy with your mpg

 

I can barely get 13...

 

Karo is "big foot". I think we are being loose with the term efficiency. For a given output of work the quadcam sixes are very efficient. Especially the 3.5l. Whereas if you make the 271 work too hard it's consumption is terrible. To achieve it's rated output WOT open loop it honks fuel for an 1800cc.

 

Glyn is correct that if you drive the crap out of the M271 it gets poor mpg for an I4. What engine doesn't get poor consumption when it's worked hard? But in normal driving it is very efficient. Also, the 2.5 M272 is a big offender. Make it work (and by god you're gonna have to) and it is horribly inefficient by even V6 standards. I couldn't manage more than 22mpg out of it on the highway. That is a huge 10mpg difference from the 32 my M271 can pull easily on the highway. OTOH I spent a week in a 204 C350 that had no problem attaining 30mpg on the highway. I like the 2.5 V6 free-revving and refined nature but it gets poor mileage by any standards and coupled with the 7G is infuritating to drive (it's either redlining every gear or constantly shifting).

 

You're doing something wrong, or there is something wrong with the car. My LIFETIME average with premium is 25MPG. On a recent trip from CA, I got a personal best of 29.4MPG driving 75-85MPH on the highway (In OR which is FAR from flat).

Karo, that is some ugly mileage, LOL.

 

The car in question was a 07 C230 7G bought CPO at 24k miles. I really didn't care for the car at all in the multiple times I've driven it. I took your advice this last time and drove it harder. I just can't like the feel it seems to have too many gears. To each his own, though. The W203 is a great car with lots of versions appealing to lots of people. I'm glad you have found the one that fits you!

Edit:

Now that you mention it, I did spend just 80 or so miles on the highway with the 2007. The average of 22 it was giving me might have been brought down by the city driving while gettingto the freeway where it was getting about 14mpg. I don't think it's too far off though as Adidas said he averages about 22.5 overall with his 2006 6mt.

 

HAHAAH.

Ok, here you go. The 3.5L can be efficient on long runs but it sucks down gas (relatively) once you start using your right foot. Nothing like an AMG but definitely can be more thirsty than the supercharged 1.8. This was on a run back from Vegas. I've done better when I didn't have my wheels and going over completely flat land up between indiana and chicago, I was coming up on 500 miles on a tank of gas and HAD to stop because my bladder was about to explode.

 

Matt, I hear what you are saying. The 7G does feel like it has too many gears sometimes, especially when driven sedately. I feel MB could have done a better job on gear spacing on the 7G. The 2.5L M272's mileage definitely takes a huge nosedive in town. That is probably why my car has a better overall MPG than most on here, because mine is 80+% highway driven. My worst tank was 17.4MPG, 22mph average speed. That tank was 90% city.

I do love my car, and it is pretty close to perfect for me. Frankly, with my heavily trafficked commute, the 2.5L has more than enough power. But, if I had to do it all over again though, I would chose an 07 C350 6MT.

 

you are not happy with your 13mpg with an sl55 ??? im getting that in my 320 !

 

I agree with Eric, city driving with the 3.5l VS highway is a whole different story. I also agree with Glyn that these engines are pretty efficient.

If you get 20 and above in city driving then that's pretty good.

Would a supercharger or a turbo help in efficiency? I heard it does. Can anyone please confirm this?

 

The whole problem with gasoline spark ignited Otto cycle engines is that they suffer pumping losses at partial load/throttle. That is why Benz developed the Diesotto.

This is why a low capacity 4 will give good economy in town piddling around where a larger six will loose out. However - load the car & go on a high speed cruise & the six will win every time. Taking this argument to the extreme with a modern, efficient engine that breathes well & the ideal is to try & run a larger engine as close to stoichiometric AF ratio or leaner at constant RPM via a CVT. The 7G tries to do this. An engine like the 272 - 350 will give huge economy leaned out & running at a constant 2800 to 3000RPM - You can't really do this with the 271 without flat spots & driveability problems. It needs more fuel to achieve smooth running & high output.

This is well illustrated in the new Prius where Toyota have taken the engine size to 1800cc from 1500 to achieve better performance without giving up economy & emissions.

The Prius is, however, a dumb vehicle with all it's complexity. Diesel engines don't suffer these pumping losses at part fuel input & a little diesel Citroen will run rings around a Prius from a performance perspective while achieving 70 mpg. I'd rather have the Citroen thanks & I don't particularly like French cars.

This is also why I object to legislators trying to impose engine capacity restrictions on OEMS - rather tell them max emissions per mile or whatever will be tolerated & let the developers achieve it as they wish. I'll bet they will do this for the average family saloon with a six cylinder, approx square, petrol engine with one small turbo of 2 to 3 litres running at close to constant RPM via a CVT or 7 or 8 speed auto.

If the turbo Diesotto can be built economically then you can have the best of both worlds & possibly reduce capacity a little over a pure spark ignited engine. Further development of Atkinson cycle engines is also possible but this would require OEMs to raise capacity to achieve a specific output.

 

Karo - the easy answer to your question is yes. The devil lies in the tuning.