PUZZLE 097 Fuel Up

There is a triangular mountain, with a road going up one side and a road going down the other.
Each road is twenty miles long.
The car can drive ten miles on each litre of fuel.
How many litres of fuel will it need to drive up to the top ob the mountain and down to the goal?

Hint 1

You don't need forty miles' worth of fuel.

Hint 2

The fuel consumption is still one litre per ten miles on the uphill slope.
You only need fuel for the distance driven.

Hint 3

Why not switch off the engine to save fuel?

Super Hint

Even with the engine off, the car will make it to the bottom of the mountain.
There's no need for fuel on the downhill stretch.

Answer for 'Fuel Up'

The answer is '2'.