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Are you all forgetting the primary force behind big truck design? Money. The least amount of that to produce the highest returns. Subsidized fuel means it is a lesser consideration. The highest costs to run a truck are: 1) fuel; 2) driver pay; 3) tires.
Government can be suborned to continue fuel subsidies on several fronts. Employees can be exploited endlessly. Tires can be capped and re-capped (so what the failure rate).
The TARE weight of the trucks I drove was 27,000 to 27,500-lbs (tractor at 18,000-lbs and trailer at around 9,000-lbs; flatbeds, mainly). The gross weight limit on federal highways is 80,000-lbs. That means that the load was (for the companies I worked for) at or near 50,000-lbs.
Can your 2700-lb eco car tow an equivalent (and last 500,000 miles?)
The pay is in how much load each truck can move (for many, but not all, types of trucking). The pay-per-mile by the customer usually depended on the value of the load; gravel or brick pays little; fancy alloy steel pays a lot.
Most OTR trucks you see average 5.5 to 7.2 (or so) mpg. Average truck has a 9 or 10 speed transmission (as most drivers aren't skilled enough to properly use a 13, 15 or 18-speed trans). Most truck engines are from around 1600 to 2,000 LBS/FT torque, and 350 to 600 HP.
Truck drivers use what is known as "progressive shifting" to work their way thru the gears; shifting at increasing rpms as the speed increases (and boost comes on).
A skilled driver is worth 30% lower fuel cost (pure profit) than one unskilled (or uncaring).
The most aerodynamic tractor is a flat front cabover. An aero tractor (KW 2000) is okay, and a conventional (Pete 379) is worst. Driver comfort, and safety generally are not so compromised -- inversely -- with a wheelbase that has the driver set back from the front axle and BEHIND the engine.
Driving a big truck is a job. Hypermiling is a joke by comparison. Truck drivers are involved in a daily grind far more dangerous than what police and firefighters are subject to. And they have no union or pension and are pretty much guaranteed to live 10-15 years shorter than average.
The only relative equivalent is not personal transportation, but a bus.
Have a look at Jay Leno's 1961 FLXIBLE with a 6V-92 Detroit. The videos are poor, but the bus originally carried 30 or so passengers at 12-14 mpg highway. THAT'S efficiency. The original configuration would probably have been an 8 or 9 speed coupled to a low HP 2-stroke DETROIT.
Some of them old bus drivers were true gear jammers. I remember in the early 70's going from northern New Mexico to Dallas with a bowlegged old cowboy in the seat -- his little boy sitting behind him -- and passing slow traffic on the shoulder when he couldn't get around them in the hammer lane. That motor never saw south of 2,500 rpm as I recall. I moved back in the seats a ways just to listen to the way he did it, hanging in the aisle to watch his decision process. I'll never forget that beat-up sonnuva . . . .
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