Around the bottom is a level line. Maybe a 1/2 inch high. Just plane 30wt oil. Some manuals say 10-30wt. Should have "oil level" stamped into the metal. You working on an old model "L" machine? Go 9n the net and find the Gravely tractor club of America. You can dig around in this section and find every manual and service book you could ever need. I hope this links correctly. GO DIGGING!!