Quote:
Originally Posted by razor02097
ere is an example....
I ride my motorcycle 120 miles then fill the tank with 1.925 gallons. That works out to 62.3MPG right? I ride another 120 miles and fill the tank with 2 gallons even that is 60MPG which is a 2.3MPG difference.
I drive my car 320 miles then fill the tank with 10.925 gallons. That works out to 29.3MPG. I drive another 320 miles and fill the tank with 11 gallons even that is 29MPG which is only a .3MPG difference.
Both vehicles the second scenario took .075 gallons more however you can see since the motorcycle had less range and took less total fuel that tiny amount of fuel made a HUGE difference in fuel economy calculations!
.075 gallons is about 1.2 cups... I don't know about you but looking in a 2" filler port on a fuel tank I can't tell if I've put 1.2 cups more in than the last time... I would assume the manufacturer has much more accurate means of measuring fuel economy than the average Joe... However I wouldn't discount the average Joe because we all know OEM will inflate fuel economy numbers...
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MPG is not a linear measurement. Gallons per 100 Miles is linear and differences can be compared accurately
120/1.925 = 62.338 MPG = 1.604 G/100M
120/2.000 = 60.000 MPG = 1.667 G/100M
That is a difference of 0.063 gallons (8.064 cups, which is just over 1 cup) of gas over 100 miles
320/10.925 = 29.291 MPG = 3.414 G/100M
320/11.000 = 29.091 MPG = 3.437 G/100M
That is a difference of 0.023 gallons (2.944 cups, which is just over a 1/3rd a cup) of gas over 100 miles.
I would not say that using .075 gallons of gas more on the 2nd tank makes a "huge difference" in fuel economy since it would only use 8 cups more gas over 100 miles. At those high MPGs, .075 gallons isn't that big of a deal, small tank or not. Its difference in fuel consumption between tanks vs the car was only 0.040 gallons (5.12 ozs, which is about 2/3rd a cup)
On the other hand, look at this example with a truck using the bike mileage to see how MPG isn't linear:
120 miles and fill up 14.925 gallons vs 120 miles and fill up 15.000 gallons
120/14.925 = 8.040 MPG = 12.439 G/100M
120/15.000 = 8.000 MPG = 12.500 G/100M
That is a difference of 0.061 gallons (7.808 ozs, or just under 1 cup)of fuel over 100 miles.
The bike had a difference of 2.338 MPG and 0.063 G/100M
The truck had a difference of 0.040 MPG and 0.061 G/100M
See how the difference in MPG doesn't mean a thing? The bike had 2.298 more MPG but used only 0.002 gallons (0.256 ozs, or about half a TABLESPOON) more fuel over 100 miles.
You have to look at fuel used over a set distance, not a distance traveled over a set volume.