After reading one of your columns it reminded me of a question that has been nagging me for a couple of years. Here in Canada the department of transportation puts out a listing for fuel economy on all vehicles sold in Canada. When it comes to diesel trucks, like the Ford Super Duty, the fuel economy information for these trucks is not available.
Why is it not applicable?
The EPA (Environmental Protection Agency) makes it mandatory for manufacturers to meet emission requirements along with producing average fuel economy ratings on vehicles sold within the states. That's the reason you see the "mpg/city and mpg/highway" on a new car or light duty truck window sticker. In Canada, the organization is called Transport Canada and allocates very similar guidelines.
Here's the catch; it is only required that a manufacturer do the fuel economy testing as per government protocol on light duty vehicles. The official definition for Heavy Duty is a vehicle with a Maximum Gross Vehicle Weight of 8,500 lbs or more. Most 3/4 and one ton pickups surpass that figure. The 1999 F-250 Super Duty pickup is right at 8,800 lbs, and the F-350 ranges from 9,900 lbs to over 11,000 lbs MGVW.
The bottom line is that fuel economy testing costs money and, if the manufacturers are not required to supply the information on the heavier trucks, they won't. So, it's not the diesel engine that causes the missing MPG figures. It's the borderline between light and heavy duty trucks.