So long as you're coasting
an engine going downhill like that will use next-to-no petrol anyway. So you're not saving much by turning it off when you're doing this. But you are highly likely to lose your brake servo with the engine off, which doesn't mean the brakes stop working completely but can get very exciting very quickly.

And when I say "Exciting" I mean watching the point of impact approaching rapidly while standing with both feet on the brake pedal and yodelling in anxiety.
(richardm, Fri 9 Jan 2009, 17:22, Reply)