The main increase to MPG from using the ECO mode is due to accelerator mapping, and gear shifting. Unless you are driving in hilly interstate conditions, where the transmission is shifting gears, youāre not going to see as much benefit from ECO mode like you would in city driving in ECO mode...
You can pull your panties out of a wad. I was kidding.
But we all know that 99.9% of all vehicles, with snorkels, are never used for that purpose, just like most people never take their 4WD vehicles off road.