Yep, to check the fuel levels, just use the switch on the control panel to toggle between main/aux. I believe each line on the digital display represents a $50 bill. To actually change which tank the motors are drawing from, you have to look in the vertical doors located in each corner of the stern (Port and SB). There you will find the valves. You are going to love this boat. Search this site and you'll find lots of good tips from guys with a lot of hours operating this 26 ft battlewagon. I have a 2000 w/ OX66 225's and love it - hopefully, with your HPDI's, you will get better than the 1.15 mpg I get.