Tires size VS hypermileage...

[yaris0985]

I change my summer tire (185/60/15) Yaris sedan for 195/50/15
But my L/100km or MPG change about 5-6% ?
my new tire are smaller but my question is if a put 195/65/15 I suposse ton win or lose MPG because the new tire are 5% bigger ? i calculated the inverse ? right ?
(sorry for my english)

[Amdkt7]

Not sure how much it will effect your actual MPG. It will affect the odometer reading, which will throw off the FE calculation. A smaller tire (diameter) will make it easier to accelerate, may even weigh a bit less, however, for the same actual speed the engine will be running faster. However, if you still drive the same indicated speed as you did before you would be actually driving a little slower, and that might improve your MPG. It's rather complicated due to the fact that the calculations are not correct based in the differences in tire sizes.