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Thread: ECO mode, usefull or not?

  1. #1
    Junior Member Steffen's Avatar
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    ECO mode, usefull or not?

    So last weekend I did a trip with the family with the XE 20t ... flat roads in The Netherlands

    Trip on sunday
    • AVG speed: 112km/h or 70mph
    • Distance: 243 km or 150 miles
    • AVG consumption 7.6 l/100km or 37mpg

    --> ECO-mode on, no traffic jams, cruise control on at 75mph, airco off !!

    Trip on monday

    • AVG speed: 102km/h or 63mph
    • Distance: 275 km or 170 miles
    • AVG consumption 6.8 l/100km or 42mpg

    --> normal mode on, 2-3 traffic jams for in total 25minutes, almost no cruise control, sometimes up to 150km/h or 100mph, airco on

    So ... why is ECO mode ECO mode? It uses more fuel it's no fun to drive, ... I don't get it. I even had some traffic jams and had higher speeds and my average consumption is less??

    What I did notice was that in ECO mode was that with the cruise ontrol on at 120km/h or 75mph the real time AVG consumption was constantly switching between +- 5,5 l/100km and 7,5 l/100km in normal mode it did not.
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  2. #2
    Super Moderator Ian D's Avatar
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    Eco mode just makes throttle changes so the power is more gradual, using less power from the engine, along with lower rpm gear changes. It’s not a less consumption mode.

    I only ever ever use normal or dynamic mode myself.
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  3. #3
    Member Dawg's Avatar
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    Once you get above 60mph .... aerodynamics and wind resistance start taking real effect
    It takes more power to get to and maintain a higher speed as a logarithmic function rather than a straight line
    ie. you need more power and fuel per one mph increase at higher speeds than you need at lower speeds

    The key is in your AVE 70mph against 63 mph - especially those periods at 75mph and cruise control uses more fuel I reckon as it races to get to set speed when you hit resume

    I found that the mpg difference between the same distance (same road and traffic conditions) was quite marked between 70mph and 80mph

    Hence the optimal speed as defined in the American restrictions many years ago was 55mph
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  4. #4
    Member chas379's Avatar
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    Quote Originally Posted by Dawg View Post
    cruise control uses more fuel I reckon as it races to get to set speed when you hit resume
    Interesting Point.
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  5. #5
    Super Moderator Ian D's Avatar
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    The gearbox with cruise control on and at the required speed actually uses less fuel than doing it yourself, the engine along with the auto box has various fuel maps to use in various conditions, one of them being cruise.
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  6. #6
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    In my previous car (Rangerover) cruise control frequently used more fuel. Reason being, say you set it to 70mph and slow down for traffic etc. when the traffic is cleared the car tries to get back up to the set speed as soon as possible and often drops down a gear and revs higher. Whereas if you are driving manually, you usually accelerate gently to get back up to cruising speed. This was a common point discussed on Rangerover forums. Cruise control can be more economical but depending on traffic and hills etc it can be more thirsty. Having said that, the Jag is a newer car and I don't know anything about the software and mapping etc.

  7. #7
    Senior Member junglejames's Avatar
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    Actual cruise control (ie not active cruise control) is more designed to sit at a chosen speed when the car has reached that speed. In which case I suspect it uses less fuel.

    Trying to claim any sort of cruise control uses more fuel just because of how it speeds up is to me, very unfair as you are comparing two different things. It is speeding you up quicker than you claim you yourself would, therefore yes it will use a little more fuel. Do a fair test, and speed up at the same rate using your feet. Now does cruise control use more fuel?
    It's like complaining that cruise control uses twice as much fuel....... Because you have set the cruise control at 130mph, but if using your own feet- "I would only drive at 30mph gov, honest".

    Then there was the person who claimed cruise control used more fuel, because it maintained a constant speed, whereas if he was driving manually, he would maintain constant power, therefore using less fuel (and also slowing down) when going uphill. That's not even mentioning how utterly annoying these drivers are.
    Are you kidding me? Cruise control does exactly what it is designed to do, and then compare it to a completely different driving style, and moan that it uses more fuel.

    What next? Complaining that a Ferrari uses more fuel than a VW Lupo when pottering around town at 30mph?
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