TurdFerguson

I have a 2006 F-150 SuperCrew and I just replaced my tires from the BFG Rugged Trial's to a set of General Grabber At/2's. I replaced with the same size tire (275x65x18) and the tread is a little more aggresive on the new set. They sort of resemble the BFG A/T's. My question is my MPG reading on my dash has dropped a good bit after replacing the tires, I dont see much difference in how often i fill up or my rpm when cruising down the highway or around town. Is there any reason for this or has anyone else noticed something like this occurring. Also during the summer months I find it difficult for my a/c to blow air cold enough to cool the cabin, do you think that would be a freon question or am I having some other issues. The a/c blows pretty cold in the morning and late in the afternoon when the temperature has dropped below 90. Any help is greatly appreciated. Thanks Again.