Poor gas mileage E320
 

I own a '98 E320 4matic wagon w/ 67K miles. I have owned the car for two years and put approx. 20K miles on it. In the last 3-4 months I have noticed that my gas mileage has gone down to approx. 16 mpg from a consistent 19-21 mpg previously. I am not getting any service lights indicating a service issue. I have replaced the air filter (which was dirty) but the poor gas mileage continues. Does anyone have any suggestions for things to check or replace to get the mileage back to where it should be.

Thanks for any feedback provided.

Sincerely, PaulM

What about the spark plugs?

Unfortunately, I would suggest looking at the mixture adaptation numbers.

MAFs (mass air flow sensors) are common issues with the 210s...this may be defective without a CEL yet. Additionally, I have had to replace multiple O2 sensors on my 1999/2001 E320s.

You may also be experiencing the 10-20% mileage decrease as a result of new 10% ethanol content in gasoline.

Wait a little longer or scan for codes (not sure if anything will come up)...don't throw the parts mentioned above at the problem since they are costly and may not be effective.

Thanks for the advice.
 

paulM

Coolant temperature above 80 deg C when car is warmed up?

as steve said look at the self adaption numbers in the live data.ideally they sould be very close to 1.00.if they have gone to 1.25 or heading in that direction replacing the MAF will usually cure the problem.[75-80k mls is common time for this]