http://www.kenworth.com/FuelEconomyWhitePaper.pdf

http://www1.eere.energy.gov/vehicles...deer_puetz.pdf


These two papers, the second one a bit dated, lists virtually every trick in the book that can be tried to get better fuel economy.


If you are focusing on just engine mods, try this:

A electrically activated valve train: this should pick up somewhere around 1 to 3% because electrically activated valves are more efficient.

By being able to program and tune the valve timing to optimize the engine can pick up 10% overall efficiency.


Eliminate the hydraulic power steering and brake boost --- replace it with a electrically activated one --- worth 1%, perhaps a bit more.


Eliminate the 6.0 HPOP and replace it with a higher pressure Common Rail Fuel Injection system --- with tuning, might pick up 2 to 3%


Convert the transmission to manual 18 speed -- eliminate torque converter losses.


Junk that big box trailer of yours and replace it with an aerodynamically optimized trailer that is 1/2 the weight and 1/2 the drag... that will pick up 10% right there.