I have not checked it that way but I have ran it to reserves then filled the tank. The most I got in was 2.67 gallons. If there is a 0.8 gallon reserve as listed the tank holds 3.4 gallons. I do not think the expansion space at the top would hold 0.6 gallons but I could be wrong. The idea has occurred to drill holes in the neck to allow more fuel into the tank.......