slktyperice

So I'm coming up on 10k miles (in the last 4 months since I got the C250), and my MPG going to work (similar driving habits and conditions) has steadily gone down from 32 to 31 to 28 or so these couple months (normalized for aftermarket wheels tires which I know reduces MPG by about 2mpg because of added unsprung weight and higher rolling resistance tires). My Service A is coming up in about 500 miles and I'm hoping that the car just needs the oil change and it'll run like new.

Is anyone else experiencing this at 5k+ miles?

Kevin82

I'm guessing you just need an oil change. Make sure to check tire pressure.

MBRedux

Keep us posted... you may be suffering early signs of the infamous Direct Injection carbon build-up issue.

jctevere

I doubt it, it sounds more like an issue of needing an oil change, combined with aftermarket tires. Also, the fact that winter blends and fuels don't provide as good MPG could also explain the phenomenon.

slktyperice

I'll let you guys know after the oil change. I don't think we have winter blends in LA. It's 60-75 degrees and sunny over here (fine it gets down to 40s at night). I adjusted my initial figure for the 2-3 mpg drop i got from aftermarket rims/tires (added unsprung weight and higher rolling resistance).

Kevin82

Could be clogged air filter too, which would make a lot of sense. Do they change that at 10k service?

AllEyesOnMe

Bumping up this post. I drive 50/50 city/freeway in Los Angeles and I am getting an avg of 23 mpg driving very conservatively, accelerating similar to a granny. This is according to my dashboard's mpg "from the start."

To get into the 30s figure, do you guys restart the mpg tracker when you are cruising on the highway? That DOES put my mpg into the 30s... But it's not the "True" mpg from the start of the commute....

Kevin82

How many miles do you drive highway and how many city one way?
I do about 2 miles city and 28 highway for my drive to work and get about 33-35mpg.

What's the total miles of your car and what brand gas do you use?

AllEyesOnMe

Total mileage on car is around 250 miles.
I use Costco gas but i don't think it'd affect it that much?
I do about 5 miles city, no heavy traffic though and slow acceleration. 15 miles freeway going at about 60 mph.

Kevin82

Let your car break in a little more. See how it is after 2 to 3 fillups of gas. ECU is still learning driving habits.

The stop and go from city driving will kill your mileage though.