On Jun 27, 2007, at 2:11 PM, Dave Tweed wrote:

>> They ran the test at ~50 MPH (55?), and used 5 gallons or so.
>> The next run was at 25 MPH, and only used 1.25 gallons

> That has nothing to do with e = 0.5*m*v^2 (instantaneous energy),
> and everything to do with the fact that most forms of resistance
> (air resistance, rolling resistance, etc.) are proportional to v^2.

Interestingly, my prius (which features instantaneous and cumulative
milage reports as well as per-trip bargraphs thereof) gets significantly
better milage on mostly highway driving (~52 mpg) than it does on
neighborhood driving (25-35mph, about 40mpg.)  I surmise that the
gas usage in the neighborhood is dominated by accelerating.  The
semi-mythical 60mpg happens on long stretches of 30-45mph roads and
(surprisingly?) rush-hour freeway traffic (where there's a fair
amount of very slow acceleration to low speeds, and similarly slow
deceleration; ideal for regenerative breaking and electric accel.)

(also interesting is that the air conditioning doesn't seem to
affect milage much, but if you need HEAT, it'll run the gas engine
to create that heat, which has noticeable impact...)

BillW
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