Axle ratios

[eagle19952]

In engineering- this is how efficient gearing is worked out:



I hope this helps

good answer

[daddysgirl]

      Actually ... in my (fairly worthless) opinion, this info is actually pretty valuable to have.  Not everyone will need it or use it even if they do, but I think that it needs to be out there.

     (Back to the long-time discussion of how much "forums" maybe used as reference in the future and how much , if any, we need to assure that info here is correct and useful.)

Well, alrighty.
My moment of brainlessness maybe wasn't as bad as I thought. Here ya go.

[TomC]

When you do less than 5,000mi a year (like the vast majority of us) fuel mileage really isn't that important. I know if Ford still made their 1,000cu/in V-8 that they put in tanks in WWII, I would seriously consider using in my bus. Gasoline engines now are as efficient as Diesels (with variable cam timing, direct injection, etc)-the only difference is the BTU content of the fuel which makes Diesels still 20% more fuel efficient than gasoline.

[bevans6]

I posted the BSFC chart for the Series 60 circa 1994 earlier, it shows similar info to what Dreadnaught posted as far as a central sweet spot for economy of that engine.  I found the last chart posted very interesting - it shows how dramatically efficiency falls off if you try to run the engine too slow.  BSFC really peaks high at low rpm, falls dramatically in the design range rpm and peaks again when running at higher rpm reflective of the increase in power you get as you run the engine faster.