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Discussion Starter #1
Hello all, forgive me if a similar post had been posted.

I have been using my c200 (1996) for like 4months now (new to MB), of all these times, I have even commented on its fantastic fuel economy, but lately, I have noticed poor mileage from this car.

here are the results of my mpg.

- filled tank and zeroed the trip clock... did 126miles (highway) with 26 litres

- another test was done on urban and it gave me less than 18 mpg

- just filled my tank now after 200miles highway and 47miles urban combined with 46 litres..

I could recall I have once made 153 miles on that car with about 7gallons, even though this is still poor compared to what I hear people say about its mpg.

PLS I NEED UR HELP.:help::help::help:
 

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Discussion Starter #2
hi all, pls assist with this.. is 15-18 mpg ok for a 1996 C200? else how do I improve this?.. what do I need to do?...
 

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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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Lots of things affect mileage:

MAF
Spark plugs
Plug coils
Grade of petrol purchased
Air filter
Fuel filter
Dirty throttle body
Vaccum leak
Blocked/cracked catalytic converter/exhaust
Oxygen sensors

The list is non-exhaustive.

I would look into MAF and spark plugs first.
 

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Discussion Starter #4
Thanks Far888. I am sure of the following.

- plugs .......replaced two months ago
- air filter......replaced 3weeks ago
- Fuel filter.....replaced a month ago
- throttle body- its clean
- Oxygen sensor... replaced a month ago.


pls where is the MAF in that car? how do I trace the vacuums?
 

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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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The MAF is in different positions for different models and years.

On my 1999 C280 it is on the passenger side when standing in front of the engine. (see attached picture with arrow)

It may be in a different location on your model year.

In relation to vacuum leaks, do note that if you do not have a pronounced rough idle, it is unlikely that you have a vacuum leak.

IF you still want to check for vacuum leaks they are black hoses which carry air to the engine and usually attached to a nozzle. Check for cracks on these hoses or improper seating on the nozzles.
 

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2001 CLK55 AMG, 2002 C32 AMG
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Lots of things affect mileage:

MAF
Spark plugs
Plug coils
Grade of petrol purchased
Air filter
Fuel filter
Dirty throttle body
Vaccum leak
Blocked/cracked catalytic converter/exhaust
Oxygen sensors

The list is non-exhaustive.

I would look into MAF and spark plugs first.
Ive replaced all of those and more that affect the air/fuel ratio and i still only get about 20 or 21 mpg :( i dont know what to do... im contemplating just putting a v8 in the car to at least get some performance with my crappy mpg lol.
 

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This is a controversial additive, but I use acetone as MPG booster. I have been using it for many years on all of my cars and t works for me. My S500 gets 11-12 MPG in city and 19-21 MPG on the freeway and overall average of 15-16MPG without acetone. With 1oz of acetone per 10gallons of gas (I use 2oz total per tank), my MPG climbs up to 13-14 MPG in the city and to 22-25MPG on the freeway, with overall average of about 17-18MPG. I have seen it climb once or twice to an astounding 27MPG, and even have pictures to prove it. Another thing to think about are parasitic drivetrain losses due to old, comtaminated and worn out fluids. I have also replaced all the fluids in my car with high end synthetics + appropriate additives for those fluids and that is the reason why my highway MPG is so good. I use Mobil 1 or Penzoil Platinum + Lubegard Engine Treatment in the engine, Redline D4 ATF + few ounces of Lubegard red ATF additive in the transmission, Redline 75w-90 gear fluid in the differential, and Royal Purple MaxGear power steering fluid.



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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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Ive replaced all of those and more that affect the air/fuel ratio and i still only get about 20 or 21 mpg :( i dont know what to do... im contemplating just putting a v8 in the car to at least get some performance with my crappy mpg lol.
Hello liquidusculade,

I notice you have very nice LARGE alloy wheels.

Unsprung weight is not a friend of good mileage.

You have to pay the price for looking good!:p
 

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Discussion Starter #9
hello FAR888, what vacuums am I to look out for? are there any vacuums connected to the transmission? pls kindly advice
 

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I am not necessarily an expert in this area Kuntash.

There are many vacuum hoses all over the engine.

You need to post a good picture of your engine so I and other members may try to identify the vacuum hoses on your car.
 

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2001 CLK55 AMG, 2002 C32 AMG
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in response to a few posts in this thread:

first off, im not trying to thread jack. hopefully just add some useful info to problems. i too have changed out all my drive train fluids to synthetics and use synthetic oil.

as for the wheels i agree, they definitely hurt the mpg. i just dont think they should hurt it as much as it is. also when i first installed the wheels i was getting about 28mpg beforehand and then about 24 after the install. since then my mpg has been getting gradually worse with a noticeable power loss.

would a vacuum leak inside the cabin say for the door locks or something cause engine issues or is that solely from the vacuum pump?

the only sensors i havent replaced affecting the performance are crankshaft position sensor, camshaft position sensor, and the knock sensor.

also next thing... i know i have a bad water pump.. its making noise. could this potentially cause poor mpg? i know i also need front wheel bearings, they make noise when i go around turns. those are on order and are getting replaced next week.
 

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1997 C280 (Cambria).
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in response to a few posts in this thread:

first off, im not trying to thread jack. hopefully just add some useful info to problems. i too have changed out all my drive train fluids to synthetics and use synthetic oil.

as for the wheels i agree, they definitely hurt the mpg. i just dont think they should hurt it as much as it is. also when i first installed the wheels i was getting about 28mpg beforehand and then about 24 after the install. since then my mpg has been getting gradually worse with a noticeable power loss.

would a vacuum leak inside the cabin say for the door locks or something cause engine issues or is that solely from the vacuum pump?

the only sensors i havent replaced affecting the performance are crankshaft position sensor, camshaft position sensor, and the knock sensor.

also next thing... i know i have a bad water pump.. its making noise. could this potentially cause poor mpg? i know i also need front wheel bearings, they make noise when i go around turns. those are on order and are getting replaced next week.

Youd be surprised at how easily mpg is effected. I have a sound system in my car, a single 15. Altogether it weighs maybe 150-170lbs, about the same as a passenger. Without that in my car, with just me in it, I make about 25mpg average (mostly city). With that in my car, and again just me, I get about 17mpg average (driving the same route). So one passenger or so can really hurt your mpg. As for the rims, I dont know much about that. Also, I have a C280 just fyi. But just saying, mpg can be greatly effected by what may seem like small things.

If your experiencing gradual performance loss and mpg loss and youv done everything thats been listed here then I have no clue what could be causing that. Usually new sparks, new oil, new belts, new air filter fix that problem. I dont know if the fuel pump has been mentioned here. But fuel pumps can go bad, and I believe there are fuel filters as well. Probably check that out.

Is your check engine light on?

And about the wheel bearings.....perhaps thats the sound Iv been hearing in my car as well? Its more pronounced while corning, but it seems to be more affected by weight on my passenger side. I had it taken to a shop when I first bought the car and they couldnt figure out what the noise was. As its completely random. Some days its silent, some days its really loud, some days its just there. It sounds like my wheel rubbing against the wheel well but I checked that first thing, and thats not it. So I eventually just called it out as some odd vibration somewhere in the vents or something and learned to live with it.

Also forgot to mention, if you do have a sound system installed, even if its a single 10 that weighs 20lbs, if its powerful enough it can cause alot of excess strain on the alternator which results in powerloss and a much poor mpg. Even if you dont notice a voltage drop, theres still extra strain on the alternator and it will still pull a little more power from the engine than normal. I believe its something like for it to produce 833watts of power it pulls 1hp from the engine or something like that. Thats a pretty big pull for an older car.
 

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there are no codes. i believe that i have done pretty much all of the normal stuff to fix this type of issue. i dont want to just continue replacing random parts so ill just wait till something actually fails completely lol.

ive been living with the mpg issue for a while now so its not going to hurt me to keep it up. ive actually been planning a v8 swap if i can find the right car for the right amount of money ill probably do it. might as well get some performance out of my poor gas millage lol.
 

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Discussion Starter #14
thanks all for your contributions, however, the effect of sound systems, and even wheel size I doubt would give a difference of 8mpg...
I am actually suspecting a vacuum leak in my own case, I intend to change the tranny sitting this weekend and and hope to get the opportunity to check all vacuums pipes in those areas.

How I hate wastage, if I can do anything to stop it, I would sure do that.,. I really envy those guys that get over 30mpg.. I say... that's waow!!.. I just wish it could be d same for me.. lol
 
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