Ignition vs. Roll start?

[sbergman27]

Engine-off coasting is not always a safe thing to do. It's not always an unsafe thing to do.

What about that time that it seemed safe, but suddenly something totally unexpected happened and it wasn't, and you and your family were killed in the terrible accident that resulted?

Safety isn't about what you expect. It's about what you don't and can't expect. And it only takes once. Think about it.

World energy usage, from fossil fuels, is about 400 exajoules per year. That's equivalent to about 3.2 trillion gallons of gasoline per year. About 100,000 gallons per second. The Yaris uses about 1/30th of a teaspoon of gasoline per second at idle. About 2 thousandths of a millionth of the average world rate of consumption. And, of course, the difference between coasting in 'D' and coasting with the engine off is effectively a fraction of that 1/30th of a teaspoon. Just the difference from engine braking. You can tap the accelerator from time to time to maintain speed, remaining in DFCO most of the time. I'm going to guess that the difference comes out to be about 1/300th of a teaspoon per second. (This assumes that engine braking is costing you about 10%. Works out to about a 3 mph/sec deceleration with your foot off the pedal. Season to taste.) Is it really worth it to save 1/300th of a teaspoon per second? 1/4000th of a gallon per minute?

-Steve