Fuel Economy

My brother and his wife just bought an SUV, surprised that my brother was "one of them" (I'm convinced that his drive to work doesn't have too much 'off-roading'), I looked up some stuff on fuel efficiency. Some interesting facts:

1. The average fuel efficiency of European cars is over 40 mpg (5.9 L/100 km), Japanese cars 45 mpg (5.2 L/100 km), and North American cars 20.4 mpg (11.5 L/100 km)^[1].
2. "The EPA tests used through 2007 do not directly measure fuel consumption, but rather calculate the amount of fuel used by measuring emissions from the tailpipe based on a formula created in 1972.
   ...
   As emissions standards have become more strict due to smog, most of the resulting numbers do not directly correspond to what people actually experience when driving. Most often, the EPA estimate of mileage is several percent higher than what the average driver manages to achieve in practice, although there are some cases where the difference is nearly 200% higher than what the average driver achieves.
   ...
   The old test^* method was particularly favorable to hybrid cars, as the driving style used utilizes far more electric-only power than most drivers will use in day-to-day driving. As such, these vehicles will see the largest decrease in fuel economy ratings - city economy is expected to drop by 20 to 30 percent, and highway economy by 10 to 20 percent."^[2]
3. "Most of these previously-cited fuel economy values are for operation on petrol, gasoline. New US light vehicles designated as flexible fuel vehicles (FFVs) running on E85 (85% ethanol, 15% gasoline) will typically achieve from 5% to 15% less fuel economy in mpg on pure E85 than when operated on pure gasoline. Older non-turbo-charged fuel-injected FFVs running on E85 will typically achieve about 25% to 30% less fuel economy on E85. Over 4 million FFVs are currently operated on US roadways as of 2005; most tend to be light trucks or van vehicles, although newer "car-shaped" high performance autos are also being introduced in the 2006 model year (e.g., 2006 GM Chevrolet Impala)."^[2]
4. "Engine shut-off becomes efficient during stops exceeding 3 seconds since fuel consumed during start is less than that consumed during 3 seconds of idle. Some manufacturers have begun developing cars that shut off the engine when not in use and automatically restart it when the brake pedal is released. Engine wear during restart is considered to be negligible."^[2]
   

• * Due to concerns over the accuracy of this method, a new test was proposed and approved in 2006 for use beginning with model year 2008 vehicles" ^[4]

To finished up, here are some fuel energy contents

Fuel type	MJ/L	MJ/kg	BTU/imp gal	BTU/US gal	Research octane number (RON)
Regular Gasoline	31.60	42.70	151,600	126,200	Min 91
Premium Gasoline	32.84	43.50	157,500	131,200	Min 95
Autogas (LPG) (60% Propane + 40% Butane)	24.85	46.02	119,200	99,300	115
Ethanol	21.17	26.80	101,600	84,600	129
Methanol	15.56	19.70	74,600	62,200	123
Gasohol (10% ethanol + 90% gasoline)	30.63	41.11	146,900	122,300	93/94
Diesel	35.50	42.50	170,200	141,700	N/A (see cetane)

^[2]

Note: The above energy values are higher heating values. For calculating actual vehicle fuel economy the lower heating value is used. The lower heating values are around 90% of the energy defined above. ^[3]

References

1. Robert Rapier, Wednesday, April 19, 2006, Fuel Efficiency and Lessons from Europe
   http://i-r-squared.blogspot.com/2006/04/fuel-efficiency-and-lessons-from.html
2. Wikipedia, Fuel economy in automobiles, 14:52, 9 March 2007 http://en.wikipedia.org/wiki/Fuel_economy
3. Automotive Handbook, 4th Edition, Robert Bosch GmbH, 1996. ISBN 978-0-8376-0333-9
4. EPA420-F-06-069, December 2006, Regulatory Announcement: EPA Issues New Test Methods for Fuel Economy Window Stickers
   http://www.epa.gov/fueleconomy/420f06069.htm