The best teacher I ever had was a man by the name of Joe Costa. He was one of the pioneer aviators and he taught me to fly, but Joe taught me so much more...

One of his lessons dealt with airplanes in particular, but can be applied to just about anything else. I was in the process of purchasing a plane and Joe told me to carefully study the logs. His lesson was that a good gauge of the future is a look at the past. A lame engine is always going to be a lame engine. Bad electronics won't get better. A leaking fuel cell will leak again. Same goes for anything mechanical. Strangely, it also goes for everything and everybody.

On to the original subject... A job (any job) requires a certain amount of energy. Let's say our economy king friend required a total of 100 hp to do whatever he was doing. His truck, your truck, and my truck would require that same amount of hp. There's a set formula to figure the fuel quantity required for the job and nothing less than magic will change it!

Fuel (diesel in this case) contains a certain amount of energy by weight. While it can be argued that there are better and worse blends of diesel, the total energy per pound doesn't differ all that much. This is something we all deal with every time we fuel our vehicles. Some loads are just better than others.

Engines in any given class share about the same thermal efficiency. While yours might be slightly better or worse than mine, they won't be all that much different... Assuming good mechanical condition. A factor of 2% would be huge. More than that get's to the point of stretching the truth.

Rolling resistance (drag) is about the only thing we can change to increase economy. Remove or smooth anything that catches air. Seal the seams. Put narrow highly inflated tires on the vehicle. Remove the a/c. Remove the alternator. Remove the accessory pad and the cooling fan. Replace all lubricants with synthetic. Blue print the engine, tranny, and the differentials.
Remove any excess weight.

Do all this and reduce the required hp to maybe 90. That's 10% by my calculations... And we all know it's impractical or impossible to do this and still have a truck. But if we could...On a truck that was running 22 mpg there might be a potential increase of 2.2 mpg!

So let's talk about our third injection event which we all seem to agree is nothing more than a slight waste of fuel to keep our cat warm and happy. Let's assign another 10% loss for that event. I doubt it's all that much, but there's another 2.2 mpg.

Add all this together and we come up with less than 5 mpg. Apply this to a vehicle that was already getting great economy and we're still under 27 mpg. Take away the changes we can't make and still have a truck... We're back to 24 mpg.

And what's most amazing... That's just about 2 mpg's better than I ever saw from any of my CTD's ('91, '94, '99, '04.5). Granted, the '04.5 is harder to keep in the higher numbers as far as economy, but I can do it. It's a matter of management and determination not to prove there are 325 horses up front.

Bottom line... I'll swap in one of the Cummins I-4's from either my Case hoe or dozer. Both pump out about 85 hp at sea level. Their potential fuel burn is about 1/4 that of the 600, so I should be able to increase my economy by a considerable number... At a top (unladen) speed of perhaps 30 mph.

I guess it's pretty obvious... I'm not buying what our friend is selling.