I've been driving this Nissan for 1867 miles now, 5 full tanks and one daily top up. My best tank is 0.81 mpg better than my worst tank, and that was 4 tanks ago! I'm busting my ass in this thing and I can't make it do anything!
My second best tank was the first tank, the short one- back when it still had mainly one and a half year old gas in it.