I am beyond frustrated!

 

UK or USA? i.e. Imperial or short US gallon.
Is the CEL Check Engine Light ON?
How do you know it is doing 13mpg? On board computer or BRIMMED tank to BRIMMED tank calculation?
Stuart

 

hi,
If you are frustrated what have you done so far?
What has the dealer (MB?) said?
Stuart

 

Stuart,
USA. No, the CEL is not on. I calculate the gas mileage by setting my odometer at 0, then when I fill up the tank I take the number of miles I've driven and divide it by the number of gallons. It's always given me between 13 and 14 mpg. I've taken it into the MB dealer twice. Each time, they say they've adjusted the timing mechanism. But it hasn't worked. I'm afraid they're not going to know what to do about it. But when you spend that much money on a car, it should work! I'm not even expecting the mileage to be 20 mpg; but something CLOSE to that would be nice!

 

Hi,
I sent a reply but it appears to have disappeared!
13-14 mpg is below what I would expect (or tolerate) as a normal gas consumption unless all your driving is short trips in city.
Since your vehicle is relatively new this problem should be covered by warranty. I would expect an overall consumption nearer 20 imp (16 US ) as an ABSOLUTE minimum.
Consumption is so dependent upon driving style. Same car, different drivers can make 30% difference quite easily. City vs Highway can make 50% difference. AirCon can make 10 difference etc.
First step is to get agreement with MB/Dealer that the consumption is as you state. Suggest a controlled test with the dealer. Full tank (to brim...not cutoff), record odometer, carry out 300 mile test, refill (to brim) AND AGREE results.
If indeed 13-14 mpg US (=17 imp) is agreed then something is wrong and MB should be more than willing and able to determine what is wrong through diagnostics or whatever.
Stuart

 

Stuart,
You rock! Thanks so much for your detailed suggestions. I'm printing them out and actually bringing your email with me when I go to the dealer. I'll keep you posted.
What part of the U.S. do you hail from?
Val

 

Hi Val,
Which part of the US!! I thought you might have guessed that I'm from the other side of the pond. Stafford England to be precise. near where all the china used to come from.

I forgot to mention. Your statement that the dealer had reset the "timing" has to be a load of rubbish. You can't reset the timing on vehicles of this type. All the setting are encoded in software. Your car is a newish car so I would be surprised if their were any updates anyway.
Good Luck,
Let us know how you get on.
Incidentally my w220 S Class 320 2000m/y (105,000 miles) returns 34mpg imperial 27 US on the motorway at constant 75mph.
Stuart.

 

Hi Stuart. I'm bringing the car in today and I'll let you know what they say or do.
Thanks so much!
Val

 

First glance, I almost blamed the brakes. But if brakes were stuck, you would notice the smell. So it's not that.

Also...I wonder what number you are dividing by. The tank holds 16.5 gallons. Full tank should go 400-500 miles.

Calculation on my car is: 440/16 = 27.5

Even if the ECU(computer) is burning very richly...mileage should not be as poor as you stated.

Chances are nothing is wrong with your car. Make sure you indeed are driving in real auto "D", NOT IN A MANUAL MODE.

So...observe the tachometer and report back. RPM should stay around 2500-2700 when you drive 65mph.

If RPM is more than 2700....you are driving in a low gear.

( Please also tell us you never move the gear stick left and right, only backward and forward. )

 

My 2002 C230K 6spd. averages (by on board computer) 19-20 MPG over several thousand miles. Most of my trips are relatively short and I like to accelerate to speed. Any trips with over 20 miles of highway driving, I usually see the fuel consumption decrease over time. I have seen numbers as low as 12-14 MPG when first starting out in the morning especially on a cold day. On long trips, 350 miles between stops I have gotten 34 MPG at 70 MPH and 29 MPG at 80 MPH.