[QUOTE 5111129, member: 9609"]yep, let her roll, gears are for slowing down or speeding up.. Learn to drive without using your breaks, at any speed above 10mph the breaks should just be for emergencies. But the huge fuel saver is speed, keep it below 50.[/QUOTE]
This pretty much describes my driving style - just generally drive slower, don't accelerate or brake hard, and use the gears to moderate speed. Also turning off the engine when you're stationary, eg at level crossings or stuck in a jam.
I find it baffling the way some people complain about the price of fuel but drive in such a way that seems designed to burn as much of it as possible as quickly as possible. And I always make a point of giving a hard stare to the idiots who sit outside Tesco in the pick-up bay with the engine running while their other half goes in and does the weekly shop. (I did once get into an argument with someone after telling them to turn their engine off while sitting in a car park, but it was too much grief and I think I was lucky not to get thumped.)
Joking aside, my current car came with one of those indicator lights that tell you when the car thinks you could change up (or down) a gear. I assume it bases its decision on speed, manifold pressure, etc.
I thought it was based on revs - at least, this seems to be the case on my car, which will give you the gear change indicator at the same revs regardless of other circumstances - eg if you're going uphill. AIUI it's a rudimentary calculation based on the amount of torque your engine can generate, and the general principle is to encourage you to change up as soon as possible.
If the electronics literally stopped feeding fuel to the engine, it would cut out. Engines don't run on nothing.
QED. If you're coasting downhill, the engine doesn't need to be running at all, so there would be no problem with it cutting itself out. It wouldn't be wise to cut it out manually, of course, but it is quite possible for a modern electronically controlled engine to cut itself out automatically when it isn't needed, starting itself up again as soon as you touch any of the pedals, and I believe that many modern vehicles do indeed work this way - they will also cut out automatically when you're stopped at the lights (I first came across this in a hire car, it was most disconcerting until I worked out what was happening).
