TurboTax has a lot of pulldown menus. If I had to GUESS what menu you might be referring to, are you mistakenly trying to enter tractor expenses in the "vehicle expense" section (i.e., the Car and Truck expense section for transportation vehicles?) i.e., does it ask for "make and model", and then has a dropdown showing weights for autos, vans, SUVs and trucks? If so, that is not the interview for tractor expenses. That's for transportation vehicles (farm cars and trucks) and has questions about odometer, commuting miles, mileage, depreciation, etc.
I'm just a fellow user--not a tax expert--but I can tell you how to navigate the program.
You can enter tractor expenses like the ones you mentioned in the regular section for "Farm Expenses" in subtopic "Common Farm Expenses.". You will see a long list of possible expense items with boxes to enter various farm expenses and one of the boxes is "Gasoline, Fuel, and Oil." There's also a box for "Repairs and maintenance" that can be used for tractor repairs as well as other property/equipment repairs that is not considered improvement. Or if you want to label the tractor repairs separately there is a subtopic "Other Miscellaneous Farm Expenses"on a different screen, where you can type in the description and the amount of any other expenses for categories not listed.
I can show you some screen images, but I don't know what product you are using (Online TurboTax or desktop software), and don't know if your business is farm (Schedule F), farm rental, or what.