Mine is very difficult to fill consistently, I have a certain pump/station that I use almost every time so I've gotten it down pretty good, but if I use a different pump with a different ground angle I will get different results. Crazy as it sounds if I have the nose of the car pointing up slightly I can get it just about full. Got 17 gallons on my last fill up which is the most I've ever been able to get in the tank, I did however run that tank lower than I have ever done before....it was LOW....poor calculation put me in a situation where I had to run the tank lower than I wanted.