Crazy Gas Saving Tip That Don't Work

By Stephen Bucaro

The other day, I was in my vehicle, sitting behind another vehicle at a stop light. When the light turned green, all the people waiting at the light where ready to go, but we couldn't, we had to sit and waste gas while waiting for the idiot at the front of the line to start his car.

With the price of gas running around $4.00 a gallon, all kinds of people are trying to make money by selling articles with tips on how to save gas. One common tip is shown below.

“ Turn off your engine if you are going to be idling for more than 30 seconds. Millions of gallons of fuel are wasted each day from idling. Your starter and battery system can handle the increased activity. ”

Unfortunately, the people writing the articles are writers, not technical people. They get paid by the word and don't want to waste time actually doing any research. And who's is going to call them on their bogus ideas? The editors who accept these articles aren't technical people either.

Before I criticize this idea, I should qualify myself. I hold a Bachelor Degree in Computer Science and spent five years working as an Engineer in Motorola's Automotive Electronics Division. Before that, I had a Diploma in Auto Mechanics from a technical school in Chicago, and I worked for a GM dealer in the Chicago Area. I'm not bragging, I'm just giving you my qualifications.

I don't know where these people live, but I live in the Phoenix area, and like every major city, there's lots of traffic and many traffic lights. I have to wait 30 seconds or more at almost every red light I hit. When the light changes to green, my vehicle better be in motion or I'll be getting the horn, and with the way people are pissed off nowadays, I could get my head blown off.

And if you turned off your engine because you're going to be idling for more than 30 seconds, you deserve to get your head blown off because your causing every body to waste time and gas waiting for you to start your car. Can you imagine if everybody turned their engine off at every stop light? That would cause massive delays and a massive waste of gas.

If you're going to be idling for more than 30 seconds, do not turn off your engine, that wastes gas, instead put your transmission in park. When your engine is idling with the transmission in park, it consumes very little fuel. That's because the crank shaft is connected to a fly wheel. The momentum of the fly wheel keeps the engine spinning smoothly. If you turn off your engine, the energy of the fly wheel (and the crank shaft counter weights) is lost.

When you restart your engine, it requires extra energy (gas) to get the flywheel and the crank shaft spinning again. Not only that, but it requires a leaner fuel mixture to get an engine started than it does to keep it running.

Now let's examine the second part of this ill-advised gas saving tip. "Your starter and battery system can handle the increased activity." I'm sure a vehicle's starter motor can handle cranking the engine over several times each day, but it won't last long if used to crank the engine over at every traffic light. If you turn off your engine every time you're going to be idling for more than 30 seconds, the starter motor brushes will fail prematurely, and you may even burn up the starter motor. A vehicle's starter motor is just not designed to crank the engine over at every traffic light.