To cruise or not to cruise

Discussion in 'General Motoring' started by Andy Mann, Mar 25, 2005.

  1. Andy Mann

    Andy Mann Guest

    Will my V70 use less or more fuel if I use cruise.
    Andy Mann, Mar 25, 2005
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  2. I don't imagine the figures would be all that significant either way,
    however I would assume that using Cruise would most likely save on fuel
    since it's monitoring/managing the speed.

    Mind you, it likely depends a lot on the terrain, weather, etc... as
    well as the speed you're cruising at.

    Your owner's manual indicates that you should use the 'E' (Economy)
    setting whilst in Cruise, rather than the 'S' (Sport) mode.

    I *love* cruise. Mind you, we also have rather straight highways 'round
    here. I wouldn't necessarily use it, say, in Ireland! ;)



    .... and Andy Mann spake, saying:
    Allan Shearer, Mar 25, 2005
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  3. Andy Mann

    Rob Guenther Guest

    In general, probably... If you really try, by using you foot to control the
    throttle you can do better then cruise control can. If you accelerate
    progressively down hills (ie - no kickdown, let the engine ramp up RPMs
    slowly... but quickly enough) then keep backing off the throttle going back
    up them - of course, don't drop lower then the speed limit... but don't let
    the tranny kick down if at all possible (might be easier on something like a
    diesel car... tho the V70 has plenty of low end torque courtest of variable
    valve timing and a LPT) then you can save even more on fuel.

    I tried cruise, no cruise but trying to save fuel, and driving normally for
    a week each on my way to work - and no cruise, but trying to drive to save
    worked the best - 5.7L per 100Kms (I was driving a diesel car), 6.0L per
    100Kms with the cruise on, and 6.1L per 100Kms driving with my lead lined

    Air-con was running at all times.

    Our 960 got 8.89L per 100kms cruising at around 115-125 kph with me and one
    person on a long highway run.... this is the best this car has got... gets
    low 9's if I drive without it on the highway... sometimes almost 11L per
    100Kms, if I really keep my foot down on the throttle. My dad gets usually
    low 9's with cruise and higher 9's without it.
    Rob Guenther, Mar 25, 2005
  4. Andy Mann

    Andy Mann Guest

    Did not realise that the air con would increase fuel consumption
    Andy Mann, Mar 25, 2005
  5. Andy Mann

    jg Guest

    Ooh yeah, takes some power to drive aircons just like in your house. Cruise
    won't slow up for hills - saves a lot of fuel doing that.
    jg, Mar 25, 2005
  6. Andy Mann

    Rob Guenther Guest

    It doesn't really use any extra fuel in my VW diesel (better A/C design and
    a smaller compressor then in the much older Volvo - as well as aerodynamics
    that favour windows-up driving).... But just letting you know the 'test
    conditions' didn't change for all three weekly runs... In the Volvo, the A/C
    makes the car drink a little more fuel... maybe 0.5L per 100kms more, and
    you can feel it sapping engine power...

    I haven't tried windows down vs air-con on (because I hate windows down...
    loud and drafty interiors aren't my idea of a nice drive - its the reason
    i'd never be a convertible owner, that and the fact I live in Canada...
    convertibles here aren't practical).... studies show its better to run
    A/C... I know my car gets best fuel economy in the fall and spring - windows
    up, no A/C, minimal fan speed, no heated seats running. Any accessory will
    sap engine power and hurt fuel economy.

    Volvo did a study and found it's safer to drive with the A/C on at 22C
    because you are at the highest level of comfort and alertness, they found if
    you go above 24-25C you get uncomfortable and reaction time is hampered,
    same goes with being really cold. May as well keep it on - air conditioning
    systems also will start to have their seals dry up if they don't run... so
    may as well run it.
    Rob Guenther, Mar 26, 2005
  7. Andy Mann

    James Sweet Guest

    On my 740 Turbo having the AC on drops the fuel economy noticeably, usually
    around 2 mpg, but when the weather is hot it's worth it. You can also really
    feel it sapping power, particularly at highway speed it just looses all the
    "kick" it normally has. I haven't seen any difference at all in economy from
    having the windows down (back when the AC was broken) but the only time I
    ever had all the windows all the way down was around town, on the freeway
    it's too windy so I'd put them down about half way and open the sunroof to
    James Sweet, Mar 26, 2005
  8. The best way to use A/C is to turn it on while cruising, and
    off while accelerating or climbing a hill or grade. You can get
    the fuel economy drop down to less than 1 mpg this way.
    I once built a switch that would allow the A/C to operate only
    when the brake light was on. Great for city driving.

    Opening the windows creates enough drag to roughly equal the A/C
    drain on economy, at least at highway speeds.

    Michael Cerkowski, Mar 26, 2005
  9. Andy Mann

    James Sweet Guest

    You wouldn't wanna do that on a 240, the AC on those is marginal at best and
    just about worthless when the engine is idling. The 240 Turbos do disable
    the compressor under boost, not sure if the 700's do but it appears not to.
    That seems to make the most sense though overall, it's only under boost that
    the extra power is really needed.

    The affect in fuel economy varies widely, the laws of physics demand that
    it'll decrease somewhat, but the design of the system and the rest of the
    drivetrain can make a big difference on how much. I'm all for good fuel
    economy but I'd rather spend a bit more on gas than have my butt glued to
    the seat with sweat.
    James Sweet, Mar 26, 2005
  10. Andy Mann

    Rob Guenther Guest

    On the 960's the A/C will be disabled if the driver is calling for full
    power, and the engine is unable to provide it - basically if you hit the
    kickdown, the A/C is off.
    Rob Guenther, Mar 26, 2005
  11. Andy Mann

    jg Guest

    That'd be fine if it wasn't too hot - it would not run long enough or
    effectively at idle, to do much cooling. And not too good when you first get
    in the hot car to go.
    Never noticed any measurable difference in any car.
    jg, Mar 26, 2005
  12. I'm not talking about running the A/C only at idle, folks!
    I meant I used it whenever I wasn't accelerating. The switch
    unit I built wasn't for this car, but would still work if the driving
    was more "stop 7 Go" than "stuck in traffic".

    I also added a rocker switch to control the A/C power, so I
    could leave that $300 thermostatic switch alone, and just hit
    the rocker. That's a good idea no matter how you use the A/C...

    Michael Cerkowski, Mar 27, 2005
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