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Old 11-13-2010, 02:35 AM   #29 (permalink)
Dr. Jerryrigger
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Join Date: Jun 2010
Location: mass
Posts: 181

The Sh*t-Box - '99 Subaru Impreza Outback Sport
90 day: 27.81 mpg (US)
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Quote:
Originally Posted by SentraSE-R View Post
It seems to me that, all other things being equal (aerodynamics, etc.) except for weight, the simple fact is it takes more work to move the extra weight. It takes more gas to do more work. All this stuff about extra glide distances doesn't come for free. It takes the extra work to get the extra glide. And since the real world isn't perfect, there's plenty of inefficiency in the engine working and the car gliding. Under some conditions, the glide side may show an advantage, but overall, day in and day out, it takes more work to move more weight, and the lighter car should get the better mpg.
This is for the most part quite true, but remember; with the exception of rolling resistance, it takes the same energy to keep a identical car of any mass moving at a constant speed. If you where to load your car with 800lbs of junk and inflated the tires proportionally (assuming they were not all ready at max pressure) you would get nearly the same mileage on a long highway trip. But if you had to stop and start many times in the trip you would suffer greatly.
With proper technique, for some people, more weight could work as an advantage for long trips at a relatively constant speed. This it not true for most people or situations, but may be for some. Notable elevation changes would add another consideration to this. I commuted down about 1000 feet over 12 miles every day. I was planning some water tanks, but I came in to a better solution; I moved in to the valley.
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