04-14-2008, 02:10 AM
I wouldn't be surprised if shutting your car off while, for example, stopped at a light is illegal at least in some places. Seems pretty dangerous and you also have to take into account holding up traffic if you're not ready to go when the light turns green. If there's 10 cars behind you waiting for you to start your car and go, that's going to waste their gas.
I also don't believe that "surging and coasting" helps at all. I now use cruise control whenever possible because I've found the car's computer's ability to keep a constant speed better than mine. Gas mileage has gone up. Surging and then coasting conflicts with several laws of physics. For example, since a body in motion will stay in motion unless acted upon by an outside force, keeping the vehicle at a constant speed take much less energy than requiring the engine to create acceleration.
As far as driving as slow as possible saving gas, I disagree with that too. A transmission plays a huge role in that. Driving at 2k RPMs in 5th gear is going to get much better gas mileage at 2k RPMs in 1st gear. Additionally, most cars are tuned to get the best gas mileage at specific RPMs. Often that's around 60MPH. Surging up to 70MPH and back down to 50, repeat... just makes sure your car is never running in its optimal range.
The biggest issue I have with the "start off slow" tactic is often drivers are oblivious to how this impacts other drivers. If you "start off slow" and try to merge onto a freeway doing 25MPH, sure you may be saving gas but the 50 or so cars doing 60MPH that have to slam on their brakes, they waste a ton of energy.
That's an extreme example, but I've seen it happen. I often see people pull out of parallel parking spots, slowing getting up to speed and mean while several cars have caught up to them and had to cut their speed in half.
I wont even get into the fact that I drive because I like to drive...
I also don't believe that "surging and coasting" helps at all. I now use cruise control whenever possible because I've found the car's computer's ability to keep a constant speed better than mine. Gas mileage has gone up. Surging and then coasting conflicts with several laws of physics. For example, since a body in motion will stay in motion unless acted upon by an outside force, keeping the vehicle at a constant speed take much less energy than requiring the engine to create acceleration.
As far as driving as slow as possible saving gas, I disagree with that too. A transmission plays a huge role in that. Driving at 2k RPMs in 5th gear is going to get much better gas mileage at 2k RPMs in 1st gear. Additionally, most cars are tuned to get the best gas mileage at specific RPMs. Often that's around 60MPH. Surging up to 70MPH and back down to 50, repeat... just makes sure your car is never running in its optimal range.
The biggest issue I have with the "start off slow" tactic is often drivers are oblivious to how this impacts other drivers. If you "start off slow" and try to merge onto a freeway doing 25MPH, sure you may be saving gas but the 50 or so cars doing 60MPH that have to slam on their brakes, they waste a ton of energy.
That's an extreme example, but I've seen it happen. I often see people pull out of parallel parking spots, slowing getting up to speed and mean while several cars have caught up to them and had to cut their speed in half.
I wont even get into the fact that I drive because I like to drive...