C 200 CDi sport MPG

[mrmjoet]

Hello!
I have just purchased a stunning C class coupe. Only problem is I'm not getting as many miles from full tank as I'd have hoped. Averaging close to 30MPG and full tank gets me 400 miles. Expected more with it being a diesel and mostly driven on motorway.
Is this the norm and if not anything I can do to improve MPG?

Thanks in advance

 

[artyman]

Unless you are particularly aggressive with your right foot you should get better than that on a motorway run, I get around 40 on average, but I have a lot of shortish runs. On a run to Scotland from South Coast recently I did 52mpg on the way up and 50.5 on a 650 mile run back averaging 60mph. What model is your C200 mines a pre Blue W204

 

[naim22]

What's your water temperature like? The thermostat is something that can damage mpg and it is not always apparent when it is failing.

Watch how quickly the car warms up, and what temperature it sits at.

It should be warm in max 15 mins and the temperature should not move from 87/92 degrees

My experience was very similar and it turned out a low tyre and the thermostat were to blame

 

[mrmjoet]

Ah I think that thermostat may be it. It's been sitting around 60-70. Is it easy and inexpensive to replace?!

 

[naim22]

Pretty simple as its on top of the engine pretty much. Disconnect the coolant pipes (one to rad and reservoir). Undo the bolts (watch out for plastic fuel lines as they are pretty brittle and are more hassle to repair). Unplug temp sender and then swap thermostats and put it all back together.

It might be a good idea to drain and refill coolant at this point as you lose some when changing the stat too.

I bought a Behr one from GSF for about 40 quid all in (it was stamped on it 92 degrees, though I think there are some 87 degree variants)

 

[V12]

Get it done ASAP, you'll see your MPG rocket and make your money back very quickly.

 

[geraldrobins]

Ive a blue efficiency 2011 c200cdi and Ive averaged 54.5 over the last 6 months, and 9000miles, with the obc showing 57.7. My driving is mainly commuting on motorway with cruise set at 72.