[redpoint5]

Just to clarify, my recommendation to take the circumference of the old tire vs new was to highlight the difference between different models of tires, not worn vs new. Different tire models will have different circumferences despite being labeled the same "size". Sites like Tirerack.com will list the revolutions per mile for the particular tire, and that number will be different between the models in the same size tire.

As our resident tire/wheel guru CapriRacer pointed out, tire design involves compromise. My point is that if a tire causes a drop in MPG, it doesn't necessarily cost more if it lasts much longer, or is cheaper to purchase. You have to factor in more frequent tire replacements, the lost earning potential of waiting at a tire shop to change the tires, and the cost of the tires themselves.

It was unclear in the OP, but it sounds like they got 80,000 miles on the LRR tires before replacing them? That is quite good.

Capri- Does a 13% drop in MPG due to tire selection sound reasonable?

EDIT:

FYI- Tirerack shows the Sumitomo turning 848 revs per mile and the Toyo at 832. The Sumitomo over-reports speed and mileage by 2%.