how to increase gas mileage
 

my 00 E430 4matic has been giving me 14mpg on highways. which to me is quite low. it advertises 20mpg. i think...
what can be done to increase the mileage ? any ideas would be helpful.
thanks in advance :)

Tuneup, tire pressures, and your right foot. A V8 4matic isn't going to return awesome fuel economy to begin with. Start with the basics.

20mpg is done in a lab under controlled conditions, which you won't be able to reproduce...If there's nothing mechanically wrong, causing the low mileage, then your foot and necessary driving only is the only way you are going to see any increase in efficiency.
My SEL is advertised for 18mpg I can really only hope for maybe 16...IIRC a 00 Mercedes gasoline sedans made it onto the cash-4-clunkers list here in Canada..

They figure that if you can afford a Mercedes, then you can afford the gas...

Are you suspecting mechanical problems, or just looking for general advice? I am not familiar with that car. I get better than advertised MPG with my car.

First of all, how do you measure the MPG? Please don't say you use the gas gauge!

What speed do you drive, what terrain and where are you?

The temperature and road conditions can affect MPG a lot.

If you really want big MPG drive behind a semi or box truck...

14 hwy on an M119?

Check your o2 sensor, coolant temp sensor (I think? Sensor on the front of the block up top, poke around on the forum), and certainly, the air mass meter

These 3 together solved same problem on my 400E

I agree with d.delano, (especially with the right foot). In addition, I get 370 miles before my fuel light somes on running 89 octane with my all season hankooks tires. These are not gas saving tires. When I change to my winter studs the fuel light comes on at 320 miles! That is 50 miles difference per tank! I was just thinking yeaterday that I can't wait to switch back.

Higher tire pressure helps too. I usually set mine at recommended max.

My '95 E420 gets 22MPG on trips and around 16 in town with the AC on and I have a heavy foot. Trip mileage was measured over a 3000 mile trip last summer. You can't get accurate mileage readings on 1-2 tanks of fuel.
Anziani

'95 E420 118K
'93 300CE 182K (26MPG)

fixed

Change your O2 sensors... My E420's mileage really dropped before changing them. They go bad long before an CEL comes on.

If or when you've gone through all of the mechanical and electrical fixes and your car is running in top condition... perhaps you'll consider changing your tires?

See

http://www.michelinman.com/tires/luxury-performance-touring/energy-mxv4-plus/

There's a chap in England who swears by them:-

http://www.honestjohn.co.uk/

To correctly determine fuel economy, fill your tank. Reset your trip odometer. Drive until you need to refuel. Fill your tank again, and divide the mileage on your odometer with the number of gallons it took to fill up your tank. The result is your avg. fuel economy.

Honest John's method includs a .22 multiplier to convert litres to gallons to arrive at MPG rather than LPG, so take note.

I doubt just tires make that huge difference in mpg. I would look to the winter formulation fuel, coupled with lower ambient operating temperatures as primary factors to lower mpg vs. just the 'tires.' Cold-weather mpg is dreadfully lower across the board.

^^^On THAT tank only.

"Average mpg," can only be learned through several tanks - reason being you will load various amounts of fuel each time you fill your tank, and, driving temperatures/conditions vary tank to tank.

Cumulative mpg over many tanks is the only way to deduce an "average" mpg.

On my SD I went to straight pipe,on other gassers,and soon my s320.I delete the cat,and use glasspak mufflers.Hard to get power out of a choked down engine.