Fuel Economy

In the sixteen years since it was manufactured, my truck has travelled some 190000 miles. Supposing an average fuel economy of 14 miles per gallon, the truck has burned about 13571 gallons of fuel. That’s a lot.

A Boeing 777-200, smallest of the 777s, has a maximum fuel capacity of 31000 gallons. That’s more than twice as much as a lot. The 777-200’s maximum range is listed as 5235 nautical miles, or some 6024 miles. Disregarding other factors, and the possible irrelevance of such limits to typical operation, these maximums suggest a fuel economy between 0.19 and 0.2 miles per gallon.

These calculations are contrived, but it should be clear that a transcontinental flight consumes more than peanuts.

Nevertheless, this comparison should not be construed as an indictment of air travel. There are millions of trucks like mine but only a handful of airliners. Furthermore, airplanes carry many passengers, and cars do not. Last but not least, cars cannot fly. Flight is intrinsically cool.

So, I leave it as an exercise for the reader to figure out how many people a 777-200 would have to carry from NY to LA to use less fuel than those people would use if they each drove a truck like mine the same distance.

Posted on Tuesday, May 13th, 2008.

2 Responses to “Fuel Economy”

Posted by Anonymous on Tuesday, June 3rd, 2008 at 11:42 AM.

Will use your calculations to try and compute an estimated fuel cost for each passenger butt plus 3 pieces of luggage assuming an average weight of 185 lbs/person luggage lg bag 70 lbs; 2nd bag 66lbs; 3 bag 42 lbs. AA is planning to fly from Chicago to Moscow which is approximately 13hrs 20mins. I believe they will fly this route using a 777-300. Anyway, guess I have nothing more pressing, ha!

Posted by EEon on Thursday, October 29th, 2009 at 2:38 PM.

Here’s an attempt: Spacetruck must travel a land route of about
2,776 miles, mostly on I-40. At 14 MPG, this works out to be 198.29
gallons of gasoline. Given a passenger capacity of 2 (people in the
bed or atop center console don’t count, since they don’t have
seatbelts), this is 99.15 gallons per person to travel from New
York to LA. No standard adjustment factor for Spacetruck weight/MPG
tradeoff is available. We’ll assume that the truck is resistant to
speed and weight-related MPG fluctuations (even though this is
patently false). The plane has a straight line distance of 2,443.79
statute miles to cover. Since there will be some distance taken up
by approach patterns, we’ll round this distance up to 2,500 statute
miles. We now make the assumption that the aircraft is at maximum
allowable weight and .84 mach cruise speed; 31,000 gallons of fuel
will allow travel of ~3,600 nautical miles (4,142 statute miles).
This assumption can be checked on the fourth page of:
http://www.boeing.com/commercial/airports/acaps/7772sec3.pdf Our
passengers are fat, sassy, and bringing thousands of pounds worth
of NYC silk pashminas home with them. 2,500 miles is 60.3% of the
777-200’s 4,142 mile assumed range. 60.3% of the 777-200’s 31,000
gallon fuel capacity is 18,693 gallons of Jet A. Next, we can
divide the total gallons used by the jet by the gallons used by
each passenger of Spacetruck: 99.1x=18,693 x=188.62 (~189)
passengers Since the typical seating capacity (seatbelts) of the
777-200 is around 300, that makes the plane significantly more fuel
efficient, per passenger, than the truck. Of course, on this trip
the truck is probably getting closer to 19 MPG, and the plane is
not likely to be maxed out for weight. Neither of these vehicles
compares favorably to the MPG/weight ratios of a diesel locomotive,
rowboat, or bicycle.