It is all about the tire, its rubber mix and its rolling resistance. I had OEM or better mileage with brand new Toyo Versado Noir, but absolutely horrible mileage when I tried new Yokohama Advan Sport A/S. Nitto Neo Gen seems to be a very similar tire to our OEM Toyo Proxes 4 Plus B, I wanted to try it, but decided to get something with a higher wear rating (which also affects fuel economy).
It sounds like touring tires are the best choice for fuel economy, but they are not great with cornering. My W-rated Proxes are wearing out slowly, they may even last 50k miles. I will be definitely getting different tires when they wear out, possibly Nitto Invo or Michelin Premier that I originally wanted to try. Nitto Motivo is a perfect choice for an everyday cheap comfortable performance tire, it will be my default choice if I fail to find another decent tire.