Help...horrible Gas Consumption!! 17 Mpg??

[mike mac]

So heres the deal, i fill my 1997 C280 with premium only, sometimes plus.

I keep up with maintenance very well and fluids flushed.

work done mechanically:
trans fluid flush
injectors cleaned
new fuel filter
Bosch platinum sparks
head gasket 38k miles ago

Out of a full 16 gallon tank i get 280 miles out of it. highway or not. my best has been 320 miles out of the tank....

eigther way i calculated 17 MPG at my worst and the usual range

its a pig like an Escalade or Hummer... does anyone have any suggestions on what the issue is?

according to Cars.com I should be getting 20 MPG city and 27 Highway...

also interested what other people get out of there tank

[jnenad16]

are the oxygen sensors original? if so, that might be the problem.

[mike mac]

Originally posted by jnenad16
are the oxygen sensors original? if so, that might be the problem.

well dumb question...you mean the O2 sensors?

i dont have an error code for them...

also wanted to add my car has been more smoky if sitting at idle...not burning oil. im thinking its running lean. idk how to fix that. i have a fairly new MAF on it with maybe 40k.

[Logic]

when was the last time you took to mercedes and have them do a run threw it? even tho you have replaced some wearing parts there may some things you might be over looking that may be causing your issue. if its running rich may be your over all cause since it will be using more gas . the plugs you have are they copper? the engines we have run better with a copper style plug and all these other fancy type plugs really dont do any better and some times do more harm then better.

[Denlasoul]

18's and 12" subs probably tacked on a few pounds.

Also, please edit your signature. It reads like shit.

[anf6789]

my C280 isn't a gas miser either, not that I drive like a hypermiler, lol. If i drive alot of highway miles, ill see 20-22, around town 17-19. No one cared about gas mileage in 1994. thats why i turn like 3k at 65, no overdrive.

[mike mac]

Originally posted by Denlasoul
18's and 12" subs probably tacked on a few pounds.

Also, please edit your signature. It reads like shit.

this has been happening for a while now before I even got the 18"s and subs... It was bone stock


Your right, my signature does kinda suck

[mike mac]

Originally posted by anf6789
my C280 isn't a gas miser either, not that I drive like a hypermiler, lol. If i drive alot of highway miles, ill see 20-22, around town 17-19. No one cared about gas mileage in 1994. thats why i turn like 3k at 65, no overdrive.

BTW I havent seen your car yet...i live like 10 min from Drexel U

[jnenad16]

usually, O2 codes wont show up until the sensors are toast. If you have never replaced them, I would bet thats at least one of your problems, if there are multiple.

[mike mac]

Originally posted by jnenad16
usually, O2 codes wont show up until the sensors are toast. If you have never replaced them, I would bet thats at least one of your problems, if there are multiple.

my friend was going to replace his O2 sensors on his BMW with O2 sensor simulators because he wants to cut his CAT. i was thinking do the same because my CAT is most likely toast as well and just put a straight pipe in or a bolt on high flow Cat.

he says o2 simulators are cheaper than the actual o2 sensors, do you think they would work nice on my car?

[black96benz]

Different car but my 96 c220 gets 29 mpg... about 425 miles before the light comes on and 467 is the farthest ive pushed it on a single tank and it took 16.2 gallons when i filled it. Car has 223,500 miles and all are highway. I would recommend new O2 sensors and some lucas fuel injector cleaner additive.

[jnenad16]

dummy O2 sensors are used to trick the car into thinking there are rear O2 sensors, but the front ones are needed for the car to operate properly and you cannot use dummies in place of those.