I'm still making assessments, But I put a GOOD grille block on, the bottom one didn't hold up well so I just left the top. It runs hotter, heats up faster, and seems to run smoother.
I don't know, but judging by how many miles I've driven and the fuel gauge position, I'd say that I'm getting between 22-25mpg's this tank. which is better than ever. More tanks will have to confirm, but since I'm on spring break and not driving, I'll say that that'll be a few more weeks