Can I get better fuel mileage

[Billdozer2]

I'm with Waterloo and Rawze.

Yes on the 13 speed (Although it's a little more work than what Cummins is saying in your previous post)

Yes on the higher rpms when loaded and rolling through the hills. And lower rpms when empty. Make the gearing work for you. Not the engine.

And no on the super singles. You won't see that much of a difference to justify the cost and the change over twice a year.

My $0.02.