tn6020

Hi everybody, I've just bough a 01 e430 4matic w/106kmi. The car was passed emission recently, running excellent, but don't know why the fuel economy is so bad: around 10mpg!
Its tires is new, thread is about 90% remaining
I had a 1999 e430 rwd before, that car I used for a 10 years and at 125kmi. it s still on 19 mpg!
So anyone has an idea? Please help! I am trying to use a bottle of fuel injector cleaner, like I had done before to my old E430 RWD, but I doubt it s not a corrected move??
Thanks in advance

dacraigo1980

Change the plugs, cheap and an easy DIY. Any check engine lights?

dacraigo1980

Also, if you just bought it, change the oil to recommended weight and see if that helps. 10 mpg city is really bad. I would expect around 16-18 in that car.

RichardM98

If it passed the smog test chances are that the plugs are okay.

So it points to something happening while the car is moving since the smog test is stationary. Check the brake system (including the parking brake) for dragging. Also, bad alignment can cause low mileage but you'd see it in tire wear if it was bad enough to cut the mileage almost in half.

Another possibility is a gas leak. Another is a speedometer error. If you are near a freeway you can check speedo using mile markers.

I assume you are calculating the gas mileage not using the instrument cluster readout. If not, do the calculation.

tn6020

alignment is good,and the car is running like a charm,one thing I noticed is the idle speed has been set a little high
about the leaking of gas tank or somewhere inside the car , I dont know how to check it out, and there is no gas smell to be noticed
I have just put in a bottle of an fuel injector cleaner, lets see the result later

Hirnbeiss

Easy method for calculating real gas mileage (assuming plenty of gas stations nearby):
wait till reserve light comes on, then head to nearest gas station
get 10 gallons of gas, reset odometer to 0
drive until reserve light comes on
divide odometer reading by 10

easy to adjust for any extra miles driven between light on and getting gas.
if you do this all the time, you also have a reliable number to let you know if something is amiss (or if you've been driving too fast).

tn6020

I used a similar method and the result is the same

CharlyE500

Change the plugs/wires, tranny oil flush, engine oil flush, fuel system cleaner Techron and very important Air filter. Also don't forget the differential oil change in this case.

Hirnbeiss

If you're getting half the mileage of your other one and can't find any obvious culprits (like the rolling resistance is infinite) then my suspicion would be clogged cats, although I would have to think you'd be getting some codes by now.
What state are you in? Does the smog check include an OBD2 hookup, or just a sniffer?

livetodrive

Cruising along on the highway at 65 mph your car should get 22 - 23 mpg. I have the same car, with almost the same miles on it.