My new truck seems to be really picky about what kind of gas I put in it. I have filled up at a Moto-Mart and a Mobil gas station, I noticed it idling really low when I pull up to a stop light or go to back it in to a spot.

I filled up at a Shell station today next to the interstate and the truck runs totally different.

I am wondering if the quality of gas varies from gas station to gas station and if it does, Where do you buy it from?