poor gas mileage

[GDawgC220]

Recently, the gas mileage on the c220 has been really piss poor.

For example, the gas needle will clear one quarter section in 40 miles...whereas before, I would be getting at least 100 miles per quarter section.

I'm lucky if I can even get 250 miles / tank whereas before, I was getting 350-375 miles / tank.

Any reason why this is? Car runs great...been a while though since the last tune up 120k major service was done at 114k. The car currently has 148k miles on it.

Would a tune-up solve this? Clogged fuel filter? Granted, the car does not get driven around as much and is really used for shorter trips around town now. But I wouldn't think the mpg would get this poor. Even on longer highway drives, it still is pretty poor in gas mileage.

Thanks for any help! :)

[Ashkan's C280]

fuel filter maybe? not sure if it would help buy you could try fuel treatments...

[Superpnoy]

i have the same problem...=\...lemme know what happens because this gas thing is low gas mileage on my car is really getting on my nerves becuase of the prices that we have here in cali

[GDawgC220]

I will if I find any further developments.

BTW, do you guys think a bad wiring harness could cause the computer to thinking more fuel is needed than it really needs? I'm assuming the wiring harness carries all this info within those wires. I've been told by my independent dealer that the wiring harness is starting to deteriorate and the computer has stored some codes but nothing to trigger a CEL...yet.

Don't have the money to drop right now to fix it...so holding out as long as I can.

[benzfan]

Exactly how would a plugged fuel filter cause POORER gas mileage? It can't. A plugged cat, on the other hand...
If the problem is not electronics related (sensor, etc), it will be the exhaust. I would start with the engine temperature sensor.

[davis449]

Have the floater in you tank checked for accuracy. That is where I would start considering this is a chronic thing with 202's.

[GDawgC220]

Originally posted by davis449
Have the floater in you tank checked for accuracy. That is where I would start considering this is a chronic thing with 202's.

I thought I remember reading something about that.

Anyway to check that myself? or a indy thing?

thanks!

[mbLova]

Yea i've been having the same problem with my 1999 c280. ive been using the reocmmended supreme gasoline and ive been getting the shittiest miles, like 220 -230 per tank and im like "yo what the hey!" im starting to think it could be time to replace the maf, and 0xy sensor and maybe even the fuel filter and change the oil, maybe this little "tune up" could help the car. ahhh i hope somebody finds a diy solution to this "problem"




1999 c280
Mblova

[alboogiee]

ummm wtf you guys talking about??? i though 200 miles/tank was normal?? well i do have a heavy foot and reguarly hit 100mph+ on my way to work thruogh back roads...but crap i would love 300+ mile/tank let ur homie know if there is a fix!! 99c230k

[fastmayte]

drive mostly city, some highway with floor, off, floor, off, wohoo, hit 110, damn cop. still get 300+ to the tank.

check your plugs, wires, airfiler, clean maf, new fuel filter, try running synthetic oil, try GUNK FLUSH to clean sludge, tire pressure, differential oil, tranny oil, O2sensors, vacum lines, engine wire harness

if u weigh over 300 lb's, that could ruin your mpgs too, :cool:

[vbrock1137]

I drove 250 miles the other day on exactly half a tank. Almost all highway at 85-90mph with a few stints above 100mph including one hitting 131mph(new top speed :D ).

It usually takes 3/4 tank for this drive. The only thing I can figure is that QuikTrip (regional store) gasoline really is as good as they advertise! (or my gas gauge broke, hope not)

[fastmayte]

yea different gas makes a big diff, like shell or chvron gives me better mpg's to the tank than mobile (or how ever it's spelt).

[alboogiee]

i've tried using different gas station's too... i am in the air force so i can get cheap gas on the base, its about a $.20 difference but i also notice a decrease in miles per tank if i fill up with shell v power or cheveron techron i can get roughly 50 mpt more, but i notice more of a power increase as well (i drive hard) like for example today, my 230k is an auto but b/c i put vpower and changed my oil today i was able to chirp 2nd gear...didnt know it was possilbe on auto but on a cold tranny it is... where this is going i dont know, but i thought that was great... have tried to replicat it with no success... okay im done....my train of thought totaly vanished...and american idol is on too

[stox]

If you're in the Air Force, get your hands on some AVGas. 100 octane, the only way to fly. :cool:

[Renn 208]

Originally posted by stox
If you're in the Air Force, get your hands on some AVGas. 100 octane, the only way to fly. :cool:

leaded gas = no good

[mbLova]

Originally posted by fastmayte
drive mostly city, some highway with floor, off, floor, off, wohoo, hit 110, damn cop. still get 300+ to the tank.

check your plugs, wires, airfiler, clean maf, new fuel filter, try running synthetic oil, try GUNK FLUSH to clean sludge, tire pressure, differential oil, tranny oil, O2sensors, vacum lines, engine wire harness

if u weigh over 300 lb's, that could ruin your mpgs too, :cool:

yea im kinda new to mb engines, and engines in general, 18, senior in hs. jus wonderin how i can check the plugs, fuel filter, maf and 02 sensors anv vaccum lines and engine wire harness. im sorry but i have no idea how to reach most of this stuff and what to look for. it would be greatly appreciated if someone could explain how to find and what to look for

thanks

mblova
1999 c280

[stox]

Originally posted by Renn 208
leaded gas = no good

Is AVGas still leaded? I thought that had been changed. My apologies then for making a real bad suggestion.

[alboogiee]

Originally posted by stox
Is AVGas still leaded? I thought that had been changed. My apologies then for making a real bad suggestion.

wish i could ge my hands on some JP8 tho