Driver affects on FE
 

This Peterson Power document contains interesting "driver" affects on FE for fleet drivers:

http://www.petersonpower.com/docs/rmh2005-5.pdf

...and, this is from page 5:

"All tires are at their least fuel-efficient point when new. As the new tire wears, the rolling resistance decreases and fuel economy improves."

Awesome, I just have a couple questions...

So super-single rear tires for semi trucks... Why are they more economical? Here's my train of thought.
I read in the article that they can weigh 800 lbs less than duallies, so obviously that's going to have a big effect on starting/stopping/accelerating---but the fuel savings is also due to less sidewall flex, right?
In a setup with duallies, you're going to have two skinny tires with sidewall flex. In a super single, you're only going to have one tire's flex to deal with.
Is this right?

The summary table on p.12 is useful. Here are two takeaways for cars:

CLIMATE:
Summer (70°F or higher) Vs Winter (25°F) -- (0.75 mpg) 13%
Wind / Terrain (On any given trip) -- (0.75 mpg) 13%
FUEL:
#2D (API 35) Vs Winter Blend (API 38) -- (0.15 mpg) 2.5%
#2D (API 35) Vs Kerosene (API 48) -- (0.9 mpg) 15%

They also claim that LRR tires are less benefit over "normal" as they approach "wear-out" ... I wonder how they know that? No citations or discussions of tests.

You all are trying to correlate from big trucks to cars in this old CATERPILLAR document. It isn't straightforward. Or, where it may be, it isn't new (to this site).

CUMMINS and KENWORTH both have White Papers on Fuel Economy which have a bit more depth (I've linked them elsewhere on this site).
.