Subject: Re: Why it's set at 55 m.p.h...

From: [email-masked] (Joe Cohoon)
Date: 23 Apr 1995 23:51:41 -0400

>> Gas mileage is FAR more dependent on the character of the driving
>> being done than on the speed.
 
This is common knowledge.  For many years the government has published both 
estimated highway and city driving mileage figures.  Much of the difference in
mileage is due to more frequent braking, engine warming up and cooling down, 
and idling at traffic lights.  Your point does not really address the question
put forth, i.e., "Can mileage be improved by driving more slowly on the 
highway?"
   
>> I get about 30mpg on my trips to Myrtle Beach, when I'm consistently
>> driving 80-85mph for all of the trip except the stretch through
>> Virginia.  My normal commute, on the other hand, nets me about 25mpg.
 
Well, your logic is faulty.  To get a more accurate analysis, drive to Myrtle 
Beach at 65-70 mph, and compare that gas mileage to the gas mileage attained 
at the 80-85 mph speeds.
 
If you do what I suggest, you may discover, "Hey, I _do_ get better gas 
mileage at 80-85 mph than 65-70 mph!"  Well, the reason for that would be the 
design of your car: factors such as gear ratios and engine performance 
characteristics are put in by the designers, frequently to achieve economy at 
high speeds.  Nevertheless, long-established principles of physics dictate 
that frictional forces increase geometrically at higher speeds.   
  
If cars were built to top out at 60-65 mph, and run economically at those 
speeds, gas mileage in the range of 60-70 miles per gallon should be easily 
attainable.  There is little market for this type of vehicle, because gas is 
cheap, and people are much more interested in getting to Myrtle Beach quickly,
and are not so interested in arriving safely.  Hey, you only go around once in
life, right?  The safety issue is a whole 'nother bone of contention, as are 
the air pollution question and the geo-politics of cheap oil. I've rambled 
long enough.  Cheers.
 
s/  Joe M. Cohoon  -- [email-masked]