what kind of gas do put in a tahoe z71 cause I swear every time I fill up two or three days later Iam filling up again

regular unleaded. Majority of Tahoe's or trucks of these sizes get about 15 miles to the gallon. On a tank of gas you're looking at about 300 miles worth of driving using about 20 gallons of fuel. Your gas miles goes down for city driving, not usually by much. Us Tahoe owners do not get the best fuel millage, that's what we get for having a heavy vehicle, with a 350 V8 engine. I love my tahoe and not worried about millage, I am disabled and do not drive much anyway.