stevie p

Hi. So I took my C300d (facelift) on its 1st 40 mile journey this morning and only got 35.8mpg. Drove from Southampton to Poole (Uk) on motorway and dual carriageway with the cruise control set at 75mph. I was expecting to see figures between 45mpg -50mpg but at the end of the trip it had only recorded 35.8mpg. Is that right?
After everything I had read about the fuel consumption on the c300d i was expecting a lot better.
Please help!

Paul9900

I have had a C300 for a number of years now and keep an eye on the mileage. At least once a year, I do a 2500 mile trip and check the mileage at each fillup. I have found that that it is extremely variable as to speed, terrain (hills), wind, loading, and what I think affects it the most, type of gasoline (Canada). I use premium gas, of course, but I often wondered if the gas stations sometimes put regular gas in the premium tanks. Anyway, after several years, I have not confirmed the variable that makes the most difference. I would say that a 40 mile trial is much too short to really evaluate mileage, owing to the variables I mentioned, as well as how the car actually calculates average mileage.

PaulR7

OP is talking about a diesel engine so the comparison with a petrol C300 doesn't really apply.
It's quite cold right now in UK so the engine takes a lot longer to heat up, the roads are harsher and tyres much stiffer. Give it a week for the temperatures to go up to double digits again and you'll probably be much much closer to 40mpg+, expect to see 50mpg during the summer only or going on a much further trip over the motorways.