[Cruz15]

According to CR the Cinturato P7 All Season Plus should give better fuel mileage than the Assurance Max.
It is rated as the lowest rolling resistance tire in our category of tires. They weigh exactly the same. Dia is .2" larger, I would have to put a pair on and test.

 

[Cruz15]

That is an opinion.
I'm telling you. the Pirelli Cinturato Strada AS from Discount Tires are wonderful, ride better, are quieter, and are delivering slightly better mileage than the OEM Goodyears did. This is my second set of Pirellis. My first was on my Sonic 1.4T Hatch, and they really woke that car up in the corners. I believe these are the P7s, but numbered for Discount only.

According to CR they have less rolling resistance than the fuel max. (Pirelli Cinturato)

 

[Cruz15]

The OEM Fuel Max is a different tire from the average off the shelf Fuel Max, it weighs 17lbs.

Wow thats seriously crazy.
Is it built differently or just less tread to start or both?

 

[Cruz15]

15 mpg is pretty big range. Did you check all four tires to make sure they are all exactly the same tire? Could be voltage on something in the fuel system? Have you had any cel s from the fuel system before? Has dealer checked for wondering voltages on the critical sensors like maf, map and oxygen sensor? Im stabbing here. Its the stuff I would look at anyway.
Have you checked how your oil pump is running how about oil pickup?