New Tires = ~Same MPG as Worn Tires
 

I just changed out a five-year-old, 37,000-mile set of Yokohama Avid tires that came from the factory on my 2015 Mazda3, for a brand-new set of Bridgestone Ecopias.

I was expecting to see a loss of fuel economy based on the widely accepted theory that new tires aren't as fuel-efficient as worn tires, all things else being equal. But I could detect no difference in my first tank's worth of fuel with the new tires, used on a highway trip of 400 miles which had no unusual winds or traffic conditions.

The new tires have deep 10/32" treads on them, compared with the 7/32" treads on the old ones. (BTW, the reason I changed out the Yokos despite the good amount of tread left on them that is that one of the tires suffered a belt separation and tread-bulge. So, I decided that since the other three are the same age and hit the same potholes as the damaged one, I felt maybe it was time.)

Since the fresh Ecopias performed as well as the worn Yokos, maybe this implies the Ecopias are going to be more fuel efficient than the Yokos as they wear in. I'll find out in the miles ahead, unless any enhanced efficiency is too small to discern, given the myriad of conditions one faces on the highway.

In any case, I was pleased to experience no loss in fuel efficiency while breaking-in the new tires.

The avid ascend serries of tires are only average rolling resistance.
Theirs avid envigor too, but it's not a fuel economy tire.
I did the reverse of what you did. I replaced ecopia with avid ascend.
I put 2 of those Yokohama tires on my leaf and saw nearly a 20% range drop.
But aside from fuel economy the avid ascend tires are a better tire in everyway.
The only way they might be tied is I have had the avid ascend on other cars and they last a long time. I would have to say they are tired or really cost in longevity, but my bet would be that the Yokohama lasts a little longer.

It was so bad I took the new avid ascend tires off the leaf after 4000 or 5000 miles and replaced them with michelin energy saver A/S. They are supposed to be more fuel efficient than the ecopia. It didn't seem like there was much of a break in.

What is the weight difference between the tires? I'm looking at new tires and the ones I really like are ~34 lbs each compared to 28 lbs for the old ones.