W202 C200 low MPG

[lukenobrains]

Hi guys just joined this forum because having a possible issue with my car!

It's a 99 C200 Elegance Auto estate.. Lovely car to drive, been reading up and it SHOULD be capable of 23mpg around town, it's actually only achieving 16!
It's really good on the motorway... Around 35ish MPG just really poor around town where it spends 90% of its life now..

It's got 150k on the clock, but has full service history... It was seafoamed a few weeks ago, had an oil change etc... But even before then it was still giving poor MPG.. Tyre pressures, got 34psi in the rears and 32psi up front...

Got any ideas what could be causing low MPG and how to sort said issues?
Was going to plug my OBDII reader into it.. But its not OBDII! Oh well...

Cheers
Luke

 

[martyz]

They are not that economical,I get 25-30 mixed driving,check your brakes aren't binding.

 

[John Jones Jr]

Haven't a clue what's causing the poor city mpg, possibly the way it's driven? But 35mpg is excellent on the M/way. You should be able to use the OBDII reader with a 38pin adaptor lead and get basic data, fault codes & live data

 

[lukenobrains]

Okay, disappointing. Kinda screwing with it really, not only did I pay a grand for a W202 when I can find W203s on ebay for cheaper...
But 16 MPG around town is actualy worse than my 2.5 V6! At this rate it'll be sold on and I'll get something a little more economical... It's my mothers daily driver and it's raping her bank account lol
Shame it's a lovely car. Will check the brakes first though


JJJ, is that something I can just get off ebay??

 

[Auto-mobile]

A dam good service would probably help, knackered air mass sensor can contribute to poor mpg, also a bad lambda sensor can cause incorrect fueling, get the fault codes read.

Oh and I would have a w202 for a grand over any w203 pre 2004

 

[lukenobrains]

A dam good service would probably help, knackered air mass sensor can contribute to poor mpg, also a bad lambda sensor can cause incorrect fueling, get the fault codes read.

Oh and I would have a w202 for a grand over any w203 pre 2004

I gave it an oil service when doing the Seafoam
I'll sort it out an air filter and fuel filter come pay day

I'll also find a 38pin adapter to plug my reader in, theres no EML or anything on the dash. How much do Lambdas and MAFs cost? Also is there a particular brand I should stick (ie OEM) or will any one from my local motor factors do?

I come from owning MGs where everything simple and cheap, this Merc is bloody expensive lol, and so far more uneconomical (alot more so, the V6 gives me 20 MPG around town) and it has a sticky brake pedal. WD40d the spring now and that seems to have sorted itself out, I just hope the car didnt start as it means to go on!!

 

[John Jones Jr]

JJJ, is that something I can just get off ebay??

Yeah, that's were I got mine I think. Five or six quid.

 

[John Jones Jr]

theres no EML or anything on the dash. How much do Lambdas and MAFs cost? Also is there a particular brand I should stick (ie OEM) or will any one from my local motor factors do?

There's no EML display. Bosch for both o2 & MAF, shop around including ebay.de for prices.

 

[mbenz1]

Also try using a full tank of Shell V-Power.petrol or BP Ultimate petrol in the car. It will help clean out gunk in the fuel system and cylinders plus lubricate the interiors of the injectors... At that mileage its will be a good idea to give the car some tasty juice instead of plain water . It could also help improve your mpg and engine performance and quietness, smoothness etc...

 

[A1EK]

You Should be getting around 20-23mpg in town as my wife used to have the same car. I drive a 230K CLK and get the same mpg with 35+ on the motorway.

A couple of things I would check are the MAF and the thermostat.

Dont assume that if you run a engine diagnostic that if the MAF does not throw back any codes then it is fine, as it could be working but poorley! as I had a MAF that was on its way out and my mpg shot right up the other way , I was getting 40+ mpg on motorway however the car would have been running too lean. IF you have a friend with the same MAF then plug it in and see if there is a different. You could also buy a second hand one on ebay as they are cheap now being so common but Do NOT buy a non OEM as they will fail!

The second thing to check is how long does your car takes to reach operating temp, with the needle in the middle? It should reach this in about 5-8 mins, if the car is running cold and takes long to warm up then it will use more fuel which may suggest why you get good motorway mpg but not in town ?

Try changing the thermostat it worked for me !