Posted by *Eric* on May 5, 2006, 9:35 pm

I was wondering what the theoretical limit was on gas mileage

Someone somewhere must have figured that out that.

The ingredients would be something like:

1. some kind of standardized vehicle shape and weight

2. a specified driving profile (ie speed) over a fixed course

3. a specific gasoline formulation (unleaded 89 octane)

4. determine the amount of energy in a gallon of the above fuel

and compute energy required to complete the course, thus

giving you computed mpg at absolutely 100% efficiency

The results might be quite enlightening, especially when the same

calculations are done for a variety of fuels (ie diesel, hydrogen etc),

graphing against speed, car body shape, weight etc

It might also debunk a lot of those wacky claims by hucksters trying to

sell you various pills/additives/carburettors etc to get "better mileage"

AND, here's a nifty benefit, it would help people to compare various fuels

so you could make a somewhat better informed decision about alternatives.

Thanks,

Eric

Posted by *rebel* on May 5, 2006, 9:57 pm

*>I was wondering what the theoretical limit was on gas mileage*

*> Someone somewhere must have figured that out that.*

*> The ingredients would be something like:*

*> 1. some kind of standardized vehicle shape and weight*

*> 2. a specified driving profile (ie speed) over a fixed course*

*> 3. a specific gasoline formulation (unleaded 89 octane)*

*> 4. determine the amount of energy in a gallon of the above fuel*

*> and compute energy required to complete the course, thus*

*> giving you computed mpg at absolutely 100% efficiency*

*> The results might be quite enlightening, especially when the same*

*> calculations are done for a variety of fuels (ie diesel, hydrogen etc),*

*> graphing against speed, car body shape, weight etc*

*> It might also debunk a lot of those wacky claims by hucksters trying to*

*> sell you various pills/additives/carburettors etc to get "better mileage"*

*> AND, here's a nifty benefit, it would help people to compare various fuels*

*> so you could make a somewhat better informed decision about alternatives.*

*> Thanks,*

*> Eric*

*>////////////////////////*

I have a French vehicle an Axiam it is a bit crap and expensive for what it

is it's saving fact is it returns 80 mile per gallon. good for rural work

steady plodder.

Posted by *Harry Chickpea* on May 6, 2006, 12:01 am

*>I was wondering what the theoretical limit was on gas mileage*

*>Someone somewhere must have figured that out that. *

*>The ingredients would be something like:*

*> 1. some kind of standardized vehicle shape and weight*

*> 2. a specified driving profile (ie speed) over a fixed course*

*> 3. a specific gasoline formulation (unleaded 89 octane)*

*> 4. determine the amount of energy in a gallon of the above fuel*

*> and compute energy required to complete the course, thus *

*> giving you computed mpg at absolutely 100% efficiency *

*>The results might be quite enlightening, especially when the same*

*>calculations are done for a variety of fuels (ie diesel, hydrogen etc),*

*>graphing against speed, car body shape, weight etc*

*> It might also debunk a lot of those wacky claims by hucksters trying to*

*>sell you various pills/additives/carburettors etc to get "better mileage"*

*>AND, here's a nifty benefit, it would help people to compare various fuels*

*>so you could make a somewhat better informed decision about alternatives.*

*>Thanks,*

*>Eric*

Do a web search and you'll eventually come across the "racers" that go

for this. IIRC, 600 to 800 mpg is the norm, but it probably is much

higher now. Ultralightweight, super-hard tires, tiny engine, slow

speeds and a lot of coasting. No provision for even much venting,

much less air conditioning.

Posted by *BobG* on May 6, 2006, 1:56 am

Rolling friction and drag is what uses the gas. Sports cars have drag

coefficients like .25. Trucks are like .9. The formula for drag is

.5*rho*V^2*S*Cd. rho is air density... 1.2 kg/m^3 about. S is the

frontal area in m^2. It takes about 15Hp to push thru the air at 40mph,

but it starts going up fast. A 100mpg car would have to be real light

(small rolling friction) and real slippery. Like maybe 1500lbs, 20HP,

and cruising at 45 or 50. And hi pressure tires.

Posted by *danny burstein* on May 6, 2006, 2:46 am

*>Rolling friction and drag is what uses the gas. Sports cars have drag*

*>coefficients like .25. Trucks are like .9. The formula for drag is*

*>.5*rho*V^2*S*Cd. rho is air density... 1.2 kg/m^3 about. S is the*

*>frontal area in m^2. It takes about 15Hp to push thru the air at 40mph,*

*>but it starts going up fast. A 100mpg car would have to be real light*

*>(small rolling friction) and real slippery. Like maybe 1500lbs, 20HP,*

*>and cruising at 45 or 50. And hi pressure tires.*

The Honda Insight - gasoline powered, hybrid - has a bunch

of crazed owners.... The _regular_ and real mpg on the

manual is typicaaly 70 or so highway. (My personal range

is normally about 55-60 on the highway with auto transmission).

Every so ofen one of the " hyper-milers " reports doing over 100 mpg.

(I've gotten as high as 75.4 on a 50 or so mile stretch. There

was a steady 30 + mile wind helping...)

--

_____________________________________________________

Knowledge may be power, but communications is the key

dannyb@panix.com

[to foil spammers, my address has been double rot-13 encoded]

>I was wondering what the theoretical limit was on gas mileage> Someone somewhere must have figured that out that.> The ingredients would be something like:> 1. some kind of standardized vehicle shape and weight> 2. a specified driving profile (ie speed) over a fixed course> 3. a specific gasoline formulation (unleaded 89 octane)> 4. determine the amount of energy in a gallon of the above fuel> and compute energy required to complete the course, thus> giving you computed mpg at absolutely 100% efficiency> The results might be quite enlightening, especially when the same> calculations are done for a variety of fuels (ie diesel, hydrogen etc),> graphing against speed, car body shape, weight etc> It might also debunk a lot of those wacky claims by hucksters trying to> sell you various pills/additives/carburettors etc to get "better mileage"> AND, here's a nifty benefit, it would help people to compare various fuels> so you could make a somewhat better informed decision about alternatives.> Thanks,> Eric>////////////////////////