Quote:
Originally Posted by CargoBoatTails
The test that I used was the simple fill up to first stop and then use a full tank of gas from a 0 trip odometer and then fill the same way and then divide the trip odometer by the gallons on the pump. This was on a Nissan Versa 4D 1.8SL CVT(which helped) going from a 225/45/17 (summer tires) to a 195/55/15 (snow tires) and consistently showed a difference of 3mpg exactly, 30 to 27 respectively. Even with a difference of 1.6" on a non CVT car you're only talking a difference of a couple hundred rpm which is negligible.

It is REALLY important when doing tests (ABA ideally) that the variables are consistent.
1. The thread is about TIRE size. It is important to understand that it means ONLY tire size. 15 to 15 etc.
2. Tests comparing different size(14, 15, 16 etc) tires means you have different rims. so weight of each rim HAS to be taken into consideration.
3. Since the rims are different sizes, then there is the consideration for the movement of MASS in and out.
4. Finally, summer tire to winter tire has some weight difference, especially on different size tires and compound difference.
5. finally, you don't say if you are factoring for the odometer being off.
YOu seem pretty clear that you don't. THe best way is with GPS mileage, it's always right regardless of tire size.
Cant really say that you 'tested' the results.
Again, MULTIPLE members have posted true tested results. A smaller TIRE, doesnot produce better mileage.