255/85/16 vs 265/75/15 realistic mpgs?

been reading some threads on "pizza cutter" style tires, 255/85/15 or 255/80/17. right now i have 265/75/16 duratracs and since i put them on my mpg's on my 2.7 4x4 went from 21-22 mpgs down to 18-19 mpgs. one of the claimed benefits of the 255's is better mpgs because there is said less rolling resistance. anyone running 255/85/16 or 255/80/17 that can chime in?
just wondering if i made the switch if i could get back up to the low 20's for mpgs again.

 

I was getting 18 max with my 255's, now I can get 21 if I try with my 265's.

 

even though the 255s are narrower which has less rolling resistance, they are also taller which takes more energy to turn them.

thats all i got

 

thats what my thought was. the 255s work out to be about a 33" tire. im thinking the better mpg statements is the return better mpgs than a standard width 33" tire due.

 

yup, the 255/85/16 is about 33.3" tall while the 265/75/16 is about 31.5"tall.

 

yup thats probably where its coming from