I already tried that and it did come up. About what I'd expect. About 1 mpg more. That's about how much it dropped when I installed them 3 years ago. So I don't think that's it but it doesn't rule out the O2 sensors either. And I'm in Texas. We haven't switched to winter formula yet.

 

maybe the station changed something in its gas....try a different station. consistently get 39-41 going 65-70 on the washington beltway. if i lessen the grip, i get up around 42-44 mpg.