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How to reach the MPG? (What speed to drive at) watch

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    If a car is stated to have 30 miles to the gallon, what speed should you drive at? Really fast or really slow? Or something moderate like 50 mph?
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    depends on the car, what is it?
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    I think I heard that efficiency improves as you drive faster, but I have a feeling on the really fast end you start losing efficiency. It should state on any promotional material what speeds they used to work out the MPG figure, and it could be assumed that going at that speed is the most efficient (as they want to get the MPG figure as big as they can). I think it's probably around 50-60mph?
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    (Original post by deploythecowcatcher)
    depends on the car, what is it?
    why does it depend on the car. It is for this question I have to answer. But it says the car's manufacturer state the car goes 30 mpg, but I have to assume a speed to continue further to obtain the final answers, so I wanted to know what speed to assume such that the car does obtain (exactly or close to) the stated mpg.
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    I would have thought revs mattered more than MPG. You're probably most efficient in a high gear at a moderate speed. Say 60? It should depend on the car because different cars have different torque bands etc., some are more geared for city driving.
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    I got a 1.8 rover 75 and i drive 12mile to college 12mile back and 10mile of that is doing 30mph so i have it in 5th gear, but am i better doing 10mile of that journey doing 70mph and doing it on the motorway? Which one will give me the better MPG??? Thanks
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    The stated MPG will be the combined MPG figure, which is an amalgamation of the urban and extra urban cycles. It's explained here. I suspect the average speed to give this figure is around 30mph. That's not to say that the combined cycle is the maximum the car can achieve - you'll get maximum MPG at around 55-65 mph.
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    I find having it in a gear where you barely need to touch the throttle is best for MPG. When fuel saving I aim to get close to peak torque using as little revs as possible. The way I see it is the more you put your foot down on the accelerator the more fuel is used.

    One of the reasons TDI's are good for economy is because they produce large amounts of torque at very low revs meaning less revs and throttle input is required most of the time. If you needed to get up a hill in a similar powered 4 cylinder n/a petrol engine the chances are you would need to use more revs and therefore more fuel to achieve the torque required to climb the hill.

    Obviously numerous other factors also affect fuel economy. As others have said most cars achieve maximum MPG at about 50-70mph, most of the cars I've driven do anyway.

    Also different cars are better in different circumstances as Topgear proved when they compared a Toyota Prius to a BMW M3 around the track (http://www.youtube.com/watch?v=dKTOyiKLARk). The Toyota was actually worse because it needed to be absolutely hammered.
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    I was told that it is 58mph + or - a few dependign on the engine

    the key to fuel economy is not teh speeed you drive it its the aggressiveness.

    so the softer you are with your accelerator and brake the better XD
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    dont push the throttle all the way down, rather touch it lightly, drive in as high a gear as possible, try not to brake, avoid traffic lights, take shortcuts, basically dont drive like an absolute douche bag
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    that sums it up, although that is an average of course and highly depends on the variables.

    1. The car (big/small/ Full of lead , Petrol/Diesel)
    2. Environmental (long trip/Short trip, Uphill/Downhill)
    3. The driver - Driving in 3rd gear at 50mph = bad plan
    4. Windows open? radio on? gadgets and other things can drastically effect fuel economy
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    probably between 50 and 60, but on a motorway this is unrealistic, so i guess as low as you can manage, e.g. 70mph, and not blasting music really loud, which i do!

    wish i had a 6th gear
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    (Original post by Yas89)
    probably between 50 and 60, but on a motorway this is unrealistic, so i guess as low as you can manage, e.g. 70mph, and not blasting music really loud, which i do!

    wish i had a 6th gear
    The volume of your stereo is irrelevant. If you have it on at any volume it uses electricity and if you turn it off it doesn't (or it just uses standby amounts - i'm not sure!).


    But as people say, it depents on the car but is about 60mph. It's more important to be smooth with your driving though. Use engine breaking to slow down, accelerate smoothly and not too hard and drive in an appropriate gear for your speed. It will do wonders for your economy.
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    (Original post by hothedgehog)
    The volume of your stereo is irrelevant. If you have it on at any volume it uses electricity and if you turn it off it doesn't (or it just uses standby amounts - i'm not sure!).
    You're using more energy with the volume up, therefore the fuel economy will be (ever so slightly) effected.

    Any electrical usage at all influences fuel economy, although some more than others. It's a bit like the whole AC thing, somewhere I heard it can steal as much as 10% of your power - depending on the car. Anywhere up to about 50mph it's actually more efficient just to have the window down.
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    Most car stereos use such a minute proportion of power it is highly unlikely you'd notice any change in your mpg.

    Aircon, heaters, and open windows/sunroof have a much greater impact.
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    (Original post by Memphis)
    You're using more energy with the volume up, therefore the fuel economy will be (ever so slightly) effected.

    Any electrical usage at all influences fuel economy, although some more than others. It's a bit like the whole AC thing, somewhere I heard it can steal as much as 10% of your power - depending on the car. Anywhere up to about 50mph it's actually more efficient just to have the window down.
    You actually don't. Energy usage is the same no matter what volume you're at.
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    (Original post by hothedgehog)
    You actually don't. Energy usage is the same no matter what volume you're at.
    How come?
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    Tidied up. Keep it sensible or I'll bin the lot.
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    I drive 15mile to college most of it doing 30mph in 5th gear then i do hit a 2national speed limits which are about 3mile at most in total! But i worked out i was doing 25mpg, but on the motorway when i do the college trip its abit shorted distance and my fuel needle doesnt move much! I do own a rover 75 and do have a gas tank in the boot, not being used atm until i get it calibrated, but is that ok? am i abit too right foot heavy?
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    i find on the motorway my mpg goes up to about 42 (highest its been) yet driving around the city on little journeys it goes to about 28. Driving anything over 75mph in my car makes my fuel gauge go down drastically, so im trying to learn to enjoy driving at slower speeds. i have a new shaped clio, 1.4 16v if that makes any difference! i think the best speed is about 60 mph for my mpg, i get obsessed with watching it change on my onboard computer!
 
 
 
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