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Diesel mpg has decreased

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Mercbenz123, Oct 28, 2012.

  1. Mercbenz123

    Mercbenz123 New Member

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    Your Mercedes:
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    Hi there
    I have a c200 cdi sport 2007 my mpg around town was around 33 and motorways was 45

    And now...

    Around town is 20 and on motorways is 26 mpg

    I have checked the oil, that seems to b fine.. What problems can affect the mpg of a car...

    Any help would be much appreciated

    Thanks
     
  2. Triv

    Triv Senior Member

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    What's it's operating temperature? Too cold and it'll be thirsty. If that's the case, it will probably be wise to replace the thermostat.
     
  3. panason1c

    panason1c Senior Member

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    Your Mercedes:
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    During dark, cold mornings/evenings, you will use more fuel due to a longer engine warm-up period and ancillaries such as heated rear window and mirrors, wipers, headlights, cabin fan, etc, put more load on the alternator which creates an extra load on the engine which increases fuel consumption.
     
  4. st4

    st4 Banned

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    Thats way off though, more than winter diesel and using more electrics. I'd wager the stat of the Mass AirFlow meter to cause that level of fuel usage.
     
  5. Naraic

    Naraic Moderator

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    So many views...

    Best thing is to get it to an Indi with STAR and get the codes read.

    If it had been the oil (though not quite sure what you expected there), the engine would have been wrecked if it was so low as to cause higher fuel consumption.

    Stop the guessing...get it read.
     
  6. Corned

    Corned Senior Member

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    Mine has started taking much longer to warm up in the last few days.

    It's the cold weather...
     
  7. OP
    Mercbenz123

    Mercbenz123 New Member

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    Your Mercedes:
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    Operating temp is 80-90 goes up and down

    Thanks for replies guys
     
  8. tode

    tode Senior Member

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    That's not right - should be strictly constant.
     
  9. OP
    Mercbenz123

    Mercbenz123 New Member

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    What would you recommend and what could be the problem?
     
  10. tode

    tode Senior Member

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    'Fraid I'm not very mechanical, but if it's a 2007, then I'd start with change of thermostat.

    Should run somewhere between 85 and 90, but stay constant once warmed up.
     
  11. grober

    grober Senior Member

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    Could be a partially blocked DPF?
     

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