Fuel consumption

[Carol Anne]

Would doing a steady 50mph on the motorway use half the amount of fuel it would take to do 100mph over the same distance?

[tigga]

Not according to the figures provided by car makers, its usually more at higher speeds though not proportionally- at 100 mph you would have a lot more wind resistance.

They usually state the best consumption rate is achieved at a constant 56 mph.

[Gnu]

The amount of fuel used depends mainly on air resistance when travelling at these speeds.  Air resistance is proportional to the square of the velocity, so travelling at 100mph has 4 times the air resistance of travelling at 50mph.

Fuel consumption would be at 50mph would be roughly a quarter of that at 100mph.  There are lots of other factors that affect the exact relationship, such as rolling resistance from the tyres etc, which gear you are in etc.

[ianess]

I don't think so but someone out there will probably have a formula for it.   On the subject of fuel economy I was taught that when the speedo needled pointed straight up then that was the most fuel-efficient speed.   That was long ago and times change.

[carolyn kus]

Nah!! probably won,t but it will take you twice as long, no good if your in a hurry!!

[pagey]

No.

Optimal speeds for cars vary between manufacturers. Most modern cars have an optimum nearer 68mph. It very much depends on engine type, gear ratios and aerodynamics.

As a thought for comparison, the Bugatti Veyron will consume �100 fuel in 50 miles flat out (252mph). This does not mean it will do 1250 miles at 10mph with the same amount of fuel.

[Cmitchell]

Don't know the answer to your question but I wouldn't even think about doing only 50mph on aANY motorway for fear of getting a rear- end shunt!

Cmitchell