To find leaks I juste clean everything up real good and then wrap the lines with paper towel as well as the pit paper towels beneath the tank. The 2 piece oil tanks are notorious for leaking at the seam. I’ve always kept all my machines with the oil injection just because of the pain in the ass factor of mixing but if you do go to pre mix just remember you will need to keep the tank for the rotary valve. The grommet on the bottom of the oil tank is another common leak point