Talk:Fuel efficient driving

What a pain
This article is very poorly written, style needs rework. F15x28 12:49, 28 July 2006 (UTC)

I think it would have been more painful if I had said anything that was wrong. Thanks to all who have made contributions to the style. David R. Ingham 05:04, 26 September 2006 (UTC)

Drag
The last paragraph seems to need work. David R. Ingham 08:16, 22 May 2006 (UTC)

Removed Incorrect Statements
I removed this:

" Driving slowly or reducing speed, before applying the brakes, reduces the amount of kinetic energy (from gasoline) that is dumped in the brakes at a stop. The equation for this is $$E = mv^2 / 2 $$ (the classical limit, for $$v \ll c$$, of Einstein's famous $$E = mc^2/\sqrt{1-(v/c)^2}$$).  That is, coasting down to half the peak speed means you have saved three quarters of your kinetic energy.  It may even let you catch a light, without using the brakes at all.  (These methods have the added benefits of not getting the front wheels so dirty and of prolonging the life of the brake pads.)"

because it is incorrect. Logically, it doesn't matter whether or not you use the brakes when stopping for a light. Both situations will dissipate the same energy, as long as you don't hit the gas. There's no way stopping differently for the light could possibly put more gas back in your tank. Also, the relativity bit is frivolous, as the world record for the fastest car ever wasn't even fast enough to affect the difference in its Newtonian energy and its relativistic energy within one part per trillion. Also, slowing down to half your speed only retains 25% of your initial kinetic energy, not 75%. 75% is the part that is dissipated.

Minipie8 02:54, 22 July 2006 (UTC)

I do see some difficulty with this passage, but I think it is more that you misunderstand it than that there are errors. I agree that downshifting wastes the same energy as the brakes do, but what I meant was throttling the engine sooner, which you agree with, or "driving slowly". The 75% is what is saved, as I said. It represents gasoline saved by using less power before coming close enough to the intersection to need the brakes. I admit that I may have chosen an unnecessary time to remind people that classical physics is only a limiting case of relativistic quantum field theory. Originally, it was just E=mc2, which I have read is the most famous equation of all, which tempted me to address the problem that non-physicists need more help to see the unity of physics. (Someone else embellished it to make the limit show more clearly, but neglected to put the subscript zero on the m.) David R. Ingham 04:46, 26 September 2006 (UTC)

Deletion of aerodynamic drag rule of thumb
I don't see the problem. This is a fairly good and general approximation and is quite significant here. I included a link that leads to discussion of where the "almost" comes from.. David R. Ingham 05:01, 26 September 2006 (UTC)

Suggested merge with Fuel economy in automobiles
My expectation is that that article will grow too long for a single article as petroleum becomes scarcer and the US comes to its senses about global warming. 69.107.62.130 03:23, 30 September 2006 (UTC)