The most efficient tire size?

[roosterk0031]

Most economical tire for me is 195-65-15, I have 3 cars that wear them so I can get all the miles possible out of them. I'll use up the last 10-15k on my cobalt being aware of my tires limits and driving accordlng. I don't expect my 15 & 21 yo to be that aware of their rubber.