Poor economy

am8631

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ok - i know these MPG threads are usually down to driving style more than anything else but im still looking for a little help.

I have just measured a full tank to full tank and got less than 300 miles out of it - worked out to 22mpg. Its only a 230k W202 and i have not really booted it but i only do short journeys which i know is not good for mpg.

But my old Audi S4 with 4wd and 325bhp got similar figures!!! So i think there might be something amiss somewhere.

Can you guys please give me a list of things to check that would effect the MPG.

I have checked the plugs and they look fine.
There are no codes
The MAF was covered in oil but i have now fixed the breather system as per the excellent write up on here. The maf was carefully cleaned with Isopropyl.
I have changed the airfilter

What else could i check guys? By the way the car has now done over 150k miles!

cheers
Andy Mac
 

jberks

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M1, Outside lane, somewhere between Leeds and Lond
Your Mercedes
Jaguar XF 3.0 S, LR Freelander 2, Fiat 500 & Fiat Panda
Not sure there is much we can do.
Tyres, tyre pressures etc but I'd guess you've checked all that. Turn off the aircon?

You mention short journeys - stop-start + cold on a heavy auto = lousy mpg. In those circumstances 22 isn't out of the way, especially if the traffic is heavy or you're in a hilly area. Remember, cruising at 50 won't use that much more fuel than sitting idling in traffic. Huge difference in mpg though. Your car, cruising at 70 will return 33-35 so pro-rata, 22 sat idling isn't that bad really IMHO. I know that you'd expect better than a big V8 but the real difference on local runs will be minimal, especially if the S4 was a manual. The 230k has to work quite hard to get a heavy car like a 202 to break inertia so oddly enough you can find that a big V8 returns better mpg under the right circumstances. (e.g. Top gear's silly prius vs M3 test). If you want better stop start returns you need something light so loss to inertia is low plus skinny tyres for low drag and a small engine for low usage during idle. Hence a nice 1.0l corsa can do 40mpg - but then you'd have a 1L corsa!

If you're really concerned, get an MOT station to do an Co2 check. If its running rich then it will show up there. Doubtful but may put your mind at rest.
 
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am8631

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  • Thread Starter
  • Thread starter
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cheers guys - care to expand on the re-map Roadhog?

Its probably just the short journeys that i do and its quite hilly. Im off on holiday tomorrow so there will be a longer drive up to the airport so hopefully i will see better mileage.
 

haggettd

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C220 CDi Avangarde Estate
I think roadhog was being mischevious!
 

Tashman

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Your Mercedes
W123-300D, W123-240D, 507D campervan, W210-E220CDI, W114-250
Fit a new air filter improves economy,
and inflate your tyres properly or even a couple of lbs above the recommended presssure.
 


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