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Change in efficiency?

  • 12-10-2009 2:03pm
    #1
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭


    I bought a 05 Saab 93 Vector 1.8i a couple of months ago. At the start I was getting 7.2-7.5l/100km.

    That’s now gone up to about 8.4-8.7l/100km over the last couple of weeks or so.

    Don’t think my driving style has changed that much and my trips are more or less the same. Only thing that’s changed recently is that I get petrol in Apple Green rather than Tesco

    What other things could cause this big change in efficiency?


Comments

  • #2
    .Longshanks.
    Registered Users, Registered Users 2 Posts: 5,718 ✭✭✭.Longshanks.


    Check tyre pressure?


  • #3
    Saab Ed
    Closed Accounts Posts: 5,374 ✭✭✭Saab Ed


    She might just need an aul service. Also all engines usually use a little bit more fuel in warm weather, you didnt move to the south of France did you? :D


  • #4
    .Longshanks.
    Registered Users, Registered Users 2 Posts: 5,718 ✭✭✭.Longshanks.


    Saab Ed wrote: »
    She might just need an aul service. Also all engines usually use a little bit more fuel in warm weather, you didnt move to the south of France did you? :D

    Judging by his signature pic...no!


  • #5
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    Tyre pressure could be it.

    Will check that next time I get near a forecourt

    Any idea what the correct pressure should be?

    Its less than 4 months since its last service. Shouldn’t need another one so soon (next scheduled one is about 9k away)


  • #6
    PaddyFagan
    Registered Users, Registered Users 2 Posts: 1,146 ✭✭✭PaddyFagan


    kearnsr wrote: »
    That’s now gone up to about 8.4-8.7l/100km over the last couple of weeks or so.

    Seeing as it's mid-October, with all the schools & colleges back any chance you're fighting you're way through more traffic?
    (Or doing more short trips? school-run??)

    Paddy


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  • #7
    .Longshanks.
    Registered Users, Registered Users 2 Posts: 5,718 ✭✭✭.Longshanks.


    kearnsr wrote: »
    Tyre pressure could be it.

    Will check that next time I get near a forecourt

    Any idea what the correct pressure should be?

    Its less than 4 months since its last service. Shouldn’t need another one so soon (next scheduled one is about 9k away)

    check the manual or the inside of the drivers door or, the inside of the fuel cap


  • #8
    Scouserfan
    Registered Users Posts: 64 ✭✭Scouserfan


    make sure to press the clear button below customise to reset trip computer so you get the current value.


  • #9
    Saab Ed
    Closed Accounts Posts: 5,374 ✭✭✭Saab Ed


    PaddyFagan wrote: »
    Seeing as it's mid-October, with all the schools & colleges back any chance you're fighting you're way through more traffic?
    (Or doing more short trips? school-run??)

    Do you know that sounds like a very logical reason


  • #10
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    I dont drive to work so stuff like schools and what not wouldnt have an impact.

    I reset the trip computer every time I top up but this doesnt appear to have any effect on the efficiency


  • #11
    bazz26
    Registered Users, Registered Users 2 Posts: 51,297 ✭✭✭✭bazz26


    I'd also take into account that since the mornings over the last couple of weeks have been colder than of late the engine takes longer to warm up an run at peak efficency, this and that the internal heating system is probably on more regularly, could contribute to the noticeable change in fuel economy.


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  • #12
    JHMEG
    Closed Accounts Posts: 7,686 ✭✭✭JHMEG


    Saab Ed wrote: »
    Also all engines usually use a little bit more fuel in warm weather,
    It's the other way around. They use more in cold weather.


  • #13
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    bazz26 wrote: »
    I'd also take into account that since the mornings over the last couple of weeks have been colder than of late the engine takes longer to warm up an run at peak efficency, this and that the internal heating system is probably on more regularly, could contribute to the noticeable change in fuel economy.

    Enginee taking longer to warm up might have something to do with it but I wouldnt have thought it would be that big of a hit


  • #14
    PaddyFagan
    Registered Users, Registered Users 2 Posts: 1,146 ✭✭✭PaddyFagan


    kearnsr wrote: »
    I dont drive to work so stuff like schools and what not wouldnt have an impact.

    I reset the trip computer every time I top up but this doesnt appear to have any effect on the efficiency

    Ahh - sounds like a "long Tem" efficency figue - my yoke (a VW) has a tiny 1 or 2 beside a number of the figures in the trip computer 1 is a short term (this trip) average and 2 is a long term average. There is some complex proceedure (holding buttons for 5 secs) to reset the long term average. But also the long term average re-sets itself from time to time (I'm guessing some buffer fills).

    So I'd guess either:
    1. Your efficency is worse than you thought, but it's only showing up now because the previous owner go a lot better figure (over a large distance) so your driving is only effecting the long term average now.
    2. The long term average re-set itself recently and will take a while to "settle down" to the true value.....

    Paddy


  • #15
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    Put a bit of air into the wheels. Think they may have needed it!

    I'll wait and see how this thank goes


  • #16
    746watts
    Closed Accounts Posts: 193 ✭✭746watts


    also worth sticking some Kataclean injector cleaner in the tank as your injectors may have carboned up a bit with short journeys reducing plume efficiency and thus higher fuel consumption.


  • #17
    demag
    Registered Users Posts: 122 ✭✭demag


    It could be the fuel you are using. I've used their diesel before and had a big loss in mpg and power too.


  • #18
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    demag wrote: »
    It could be the fuel you are using. I've used their diesel before and had a big loss in mpg and power too.

    Apple Greens or Tescos?


  • #19
    demag
    Registered Users Posts: 122 ✭✭demag


    The apple green stuff, I wouldn't use it again.


  • #20
    Absurdum
    Closed Accounts Posts: 4,445 ✭✭✭Absurdum


    kearnsr wrote: »
    Only thing that’s changed recently is that I get petrol in Apple Green rather than Tesco

    Give Esso or Texaco a try for a couple of tanks and see if it makes a difference, I bet it does ;)


  • #21
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    Absurdum wrote: »
    Give Esso or Texaco a try for a couple of tanks and see if it makes a difference, I bet it does ;)

    On my wallet!


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  • #22
    mcwhirter
    Closed Accounts Posts: 1,432 ✭✭✭mcwhirter


    Is the air con unit on all the time, uses a lot of fuel more in petrol than diesel engines in my experience.
    Also I have tried apple green and shell and there is no difference in my diesels mpg. Haven't tried esso yet


  • #23
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    mcwhirter wrote: »
    Is the air con unit on all the time, uses a lot of fuel more in petrol than diesel engines in my experience.
    Also I have tried apple green and shell and there is no difference in my diesels mpg. Haven't tried esso yet

    air con is on from time to time but no more than usual


  • #24
    Gary ITR
    Closed Accounts Posts: 16,801 ✭✭✭✭Gary ITR


    Any extra weight in the car? Have you put on a few pounds?


  • #25
    EPM
    Closed Accounts Posts: 13,822 ✭✭✭✭EPM


    Onkle wrote: »
    Any extra weight in the car? Have you put on a few pounds?

    Bodies in the cellar boot?


  • #26
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,231 Mod ✭✭✭✭godtabh


    EPM wrote: »
    Bodies in the kitchen boot shallow grave?

    some one called me a fat bastard

    Boot is more or less empty but again nothing has changed over the last month


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