My Vehicle I bought is a 2000 Chevy, its a 4 cylinder manual flex fuel. I put in 20 bucks and it gave me around half a tank, but I drove exactly 40 miles and went through quarter of a tank. Now, I had a code P0300 and it was a pain but I changed spark plugs, and wires, and both coil packs, its gone now. Im not exactly sure what else can heavily affect gas milage but I'd appritiate help. Thank You.