Off the top of my head, I think it is 18 gallons, but I have never put more than 17 gallons of fuel into mine... To be sure, you could flip through your owners manual.

 

I've heard from 17 to 18.5 from different sources. So I figure about 18.

And why did I get moved down to "Junior Member"?

 

Checked the manual and it says 18.

Pretty sure Ive never put more than 16 or 17 gallons in it and ive run it for 2 days with the gas light on before filling.
Ill take the manual's word for it though.



Now I guess I have to do some math. Its been a while since Ive actually had to think.