1 gallon. I bought this thing with no manual and can't read Japanese...didn't know where the dipstick was. I was having problems with the hydraulics and wanted to make sure it had enough oil, so I dumped in a whole gallon. I later found the dipstick and now see that it is way over the full mark. The hydraulics problem was resolved by making sure all of the switches are set correctly on the control box. I figured it was similar to power steering reservoir where too much doesn't hurt anything, but wanted to make sure.