more mpg from bridgestone B381

[moonmonkey]

how many mpg more will i get with "the best LRR tire" the bridgestone B381 ,,as compared to my present LRR goodyear viva-2 tires (which netted me no gain) and yes they are well past break in at 30+k miles, just wondering if i'll ever recoupe the extra $180 or so the bridgestones cost over maybe the sumitomo HTR200 also a lrr tire. p175/65r14 on my echo.