yes so ive been told, also on motorways, because youre not changing gear so often

Believe it or not, YOU CAN. You're using less power by going slower, because you're not consuming much fuel for acceleration power.

No, You need to be in the highest gear (so you will be driving quite fast) but not have your foot hard on the accelerator (so that the revs should be low). - that way you are driving fast with low revs! Because the highest gear (usually 5th) is the most efficient. Also: to slow down dont hit the breaks, release the accelerator (earlier) and let the car slow down with its own momentum. These are the 2 basic parts of efficient driving (there are more, but its dinner time now and so I cant finish the answer).

I proved to myself many years ago I can drive 60 mph (almost 100kph)and get better fuel economy and the time difference on a long trip is generally under a half hour more. You will also arrive less tired and stressed. I have been on long trips (driving from Colorado into Texas) and have had people pass me up to 11 times in one day. reason they must stop more often for fuel. I just drove from south Texas to Tenn and back aprox. 2700 miles and used 90 gallons of fuel and averaged for the trip 30 mpg driving 60 mph. Driving time was about 20 hours each way. So yes, driving 60 mph you can save fuel on the highway. Also, when starting from a stop, you can save a great amount of fuel by lightly pressing the accelerator peddle. You accelerate almost as fast as the person who presses the peddle down hard but you burn much less fuel...I get over 21mpg city driving as well. I hope this helps.

Cars are not geared to be efficient by driving slow. The engine needs to be in the "optimum" RPM range for best fuel efficiency. Any automatic transmission will drop into its highest gear when the accelerator is not being stepped on, however, the engine RPM's may be too low for the fuel to be burned most efficiently, and additional fuel will be wasted when the car encounters an incline, requiring the gas pedal to be pressed and the car dropped into a lower gear with the engine revved in order to maintain speed. Since an automatic is going to drop into it's highest gear at any opportunity it can, the engine needs to achieve the rpm range which provides for the most efficient fuel burning in that gear. Generally, For modern aerodynamically enhanced cars, the most efficient average speed is more in the range of 65 mph or even higher. There is a reference to this on tip 27 on this page of 33 Gas Saving Tips - http://www.funandsafedriving.com/content-11.html

Yes. Energy = force x distance. Therefore, decrease the force and you decrease the energy used therefore you need less gas. Force = mass x acceleration therefore decreasing the acceleration decreases the force and energy. However, a certain amount of force is necessary to overcome wind resistance, friction and the fact that you actually do want to get somewhere faster than walking. Next, we have gears. Like the other guy said, you want to be in top gear. Do, say, 40mph in first and your engine will spin very fast. Do 40mph in fifth and your engine will spin very slow. Since every rev of the engine burns petrol, less revs mean you use less petrol. Also, what is your throttle angle? i.e. how far have you pressed your foot on the accelerator? The harder you press it, the more petrol goes into the cylinders on each rev so there is no point revving high in a low gear, unless you need it to go up a hill. Also, engines are tuned to have maximum efficiency at a certain rpm. Best off keeping at that position if possible. Another note on acceleration: It doesn't take much energy to sit on the one speed - all you need is to overcome a little friction and wind resistance. Most of your fuel goes in stopping and starting. If you can minimize slowing down and speeding up then you'll save big time. The worst mileage I got from my last motorbike (Suzuki GSX-750) was about 40mpg around town - heaps of speeding up and slowing down and dragging everyone off. The best mileage I got was 71mpg in the country, with a heavily loaded bike sitting on a constant 100kph (= 62.5mph). Sit on the one speed for best results. I guess the point is: take it easy, be bland, don't go overboard. Stay in top gear unless the revs are too low and the car is labouring. A little accelerator is good, too little can also be inefficient. No sudden changes in speed.