Car petrol consumption

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  Daabido on 21/12/2013 - 20:12

  There will be a point beyond which the maximum efficiency decreases. Obviously it depends on your particular car, but I remember reading once that about 90 kph was the ideal for efficiency and that at 110 kph you use 25% more fuel.

  http://www.livesmartbc.ca/attachments/fuel_efficiency.pdf

  • 

    retiredfeline on 21/12/2013 - 20:14

    Yeah, that's what I remember too. At higher speeds, air drag becomes a significant loss.

  • 

    Archi on 13/01/2014 - 10:06

    that would also depend on a cars engine capacity as well.

    1.5lt 4 cylinder engine will be different to 3.0lt 6 cylinder engine. both cars will be travelling at the same speed but the RPM will different a smaller engine will need to work harder to maintain that speed compared to a V6, but the V6 may use an excess amount of fuel because it simply has a larger engine.

    too many variables. you would need to experiment with you own car and find what it's maximum efficiency threshold would be.

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  Tuba on 21/12/2013 - 20:32

  Depends on the road (incline, surface), car, engine size, torque, gearing, wind and probably a heap of other stuff. Mine chews the same at 100 as it does at 120 (any difference is negligible). At 90 it would chew less on flat road, unless I hit hills. By being at 110 say, I have the car in its torquey range and hills dont seem to effect it much. At maybe 90, I need to press the pedal harder which will chew more fuel.

  But there would be a point for a given car where excess speed is using more fuel. And a point where going slower will use more fuel, ie: doing 70 kmh along a highway. Mine would use less fuel doing 100 for 4 hours, than it would to cover the same distance at 70.

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  _Bruce_ on 21/12/2013 - 22:41

  Your question is really hard to understand, but bear in mind that petrol consumption is measured over distance not time. So using more at 110Km/H doesn't mean you are using more for each Km travelled.

  For most cars and conditions 80Km/H is the ideal speed.

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  pao2x on 21/12/2013 - 23:21

  Yes slowing down saves fuel when someone is hypermiling (longest distance on a tank) they usually never go beyond 40kph. A speed of 100kph to 110kph can mean a 10% loss in fuel efficiency.

  http://www.biofuels.nsw.gov.au/biofuels_faq/e10_fuel_economy

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    tonyjzx on 22/12/2013 - 01:02

    yeah but a lot of this is about what you're willing to pay

    ie. my car does something like 7 litres per 100 sitting at 100km/h

    10% more is 7.7 litres… yeah i'd be willing to pay that to get there quicker

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  StuffnStuff on 22/12/2013 - 09:03

  Years ago all the specs on fuel efficiency was down at 56MPH/90KMH. Not sure if this has changed. But I'm sure if you look online at a car manufacturers website they will have fuel efficiency figures that will state at what speed you can expect that figure.

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  donga100 on 22/12/2013 - 09:54

  Keep in mind that you may be breaking the law if you drive too slowly.

  NSW: http://www.mynrmacommunity.com/motoring/2013/05/16/driving-b…

  According to the NSW Road Rules you cannot drive so abnormally slowly that you cause an obstruction.

  WA: http://www.transport.wa.gov.au/mediaFiles/licensing/LBU_DL_B…

  Driving too slowly can cause dangerous situations on a freeway, so you are required
  to travel at a speed that is no more than 20 km/h below the posted speed limit.

  • 

    Cheeper on 22/12/2013 - 11:09

    +1

    I used to rush on trips once, now I enjoy the journey. Much better :-)

    If you are serious about economy then re-think the F1 take off from the lights so you can get to the next one just down the road before anyone else. That ego boost costs…

    • 

      donga100 on 22/12/2013 - 11:13

      +1

      Good point. Accelerating more gradually saves lots of fuel.

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  coyney on 22/12/2013 - 11:43

  If you want to conserve fuel, then don't use your brakes.

  • 

    Tuba on 22/12/2013 - 12:33

    Or push the car everywhere.

  • 

    Cheeper on 24/12/2013 - 11:24

    +1

    Make sure you have good comprehensive insurance… :-(

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  onlyletters on 09/01/2014 - 12:24

  The more aerodynamic your vehicle is, the better your fuel economy is, and if you've done physics at school you'll know that it takes much more energy to propel a vehicle from a standstill than it does when its already rolling so you could roll up to the lights in the attempt to take off again at a rolling start (just remember never to take your eyes off the road when rolling forward)

  I think that buying a Turbo Diesel vehicle will pay itself off with the current petrol prices, take a look at the TDI vehicles provided from VW, they make good cars.

  Research has been done, I've read somewhere that the most fuel economical speed is 80km/h. Good luck ;)

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  Archi on 13/01/2014 - 09:54

  I think there is threshold where increased speed will provide more efficiency and decreased speed use more fuel. it will be different in everycar

  but there are way too many variables to compare. you would need 2 exact same cars driven in the same weather conditions at different constant speeds in order find out exactly and even that would probably be inconclusive.

  too many things affect fuel efficiency but there are some proven tips that can save you fuel.

  -maintain good tyre pressure
  -slow acceleration rather than trying to race the quarter mile every time you are at the lights
  -try maintain a constant speed
  -avoid hard breaking (because that will result in more acceleration)
  -a regular serviced car (oil filter and air filter change)