Saving gas

In a magazine article on being “green” it states that it is more efficient to turn the car off and back on than to leave it idling for 10 seconds or more. Is this true? I think this was a topic on cartalk a couple of weeks ago.

If you ignore a few factors that may be right. Personally on a gasoline car I would go for something closer to 30 seconds. As long as you don’t overdo it to an extreme, it really makes very little difference. I suggest you don’t try this trick at traffic lights as it is likely to disrupt traffic. Only apply it when stopped for things like someone running into the store for something.

The hybrids that turn the engine off have starters and batteries designed for heavy duty use and they don't have the delay factor since they can start off on electric.  

 Diesel engines are more efficient at idle so they would be far longer to the break even point.

While no one can predict how long a starter motor will last, adding lots more “starts” to an engine throughout the day can only raise the probability that you’ll need to replace your starter sooner rather than later.

All it takes is one starter replacement to wipe out all your gas savings. Use this habit judiciously.

Ten seconds is too insignificant an amount of time to save any measurable amount of gas. It probably wastes gas because of the extra amount needed to restart and recharge the battery.

The author has the right idea of shutting down when stopped for a while, but don’t take this particular tip too seriously.

As far as disrupting traffic is concerned, most all modern cars restart almost instantly and if they don’t, you have bigger problems that need to be addressed anyway.
If you are the third or more car in line at a red light, you get plenty of time to get your engine restarted before you can actually move.
If I am the first in line, I watch the green light of the cross traffic, when it turns yellow, I start my engine, I hold up nobody.
If every cell phone zombie and morning paper reader could be converted into an engine-off-switcher instead, there would be far less traffic disruption.

It might save a very minor amount of gas (but I think it would need to be 30 secs or more), but I wouldn’t do it because of the wear and tear on the starter, ignition switch, etc (not to mention the damage caused when folks try to restart a running car). Hybrids are designed to do it, so it’s not an issue with them. I wouldn’t do it because of the possible traffic problems. There’s much more gas to be saved by concentrating on your driving technique. Forget about this.

I ride a 2001 Kawasaki ZRX1200 motorcycle and lately, I have been experimenting with switching off the engine whenever it is not actually propelling the bike. This includes downhills and coasting toward stop lights as well as waiting for red lights. Because I try to arrive at red lights so that I am still moving when they turn green, I don’t actually use the electric starter that much more, I just let out the clutch to restart and use the kill button next to the throttle to kill the engine.
What has this done to my gas mileage? It has increased it from 45~48 to around 55mpg. I used to get about 180 miles on a tank before I had to switch the fuel petcock to reserve and now it is about 230 miles. It’s like a bonus commute to work with every tank of gas.