 half a tank i can put it in most of the time i'm filling up my diesel at about a quarter tank somewhere around there quarter tank sometimes less because i like my gauge actually i still actually have six gallons left when it says empty so when it hits around a quarter i i did that on purpose because i ran out a couple times so i moved my gauge when it says full it's right on f it used to be past it like some cars sure yeah i put it right on f and then i ran it out when it was on empty so i knew how many gallons were left because i had to have my wife didn't