I am not sure on the state laws of Oklahoma- do you know if you can distill fuel legally there?
Did you buy your still from a company that reports still sales to the TTB? If so then your name is already registered with the TTB and I personally would get a fuel permit if that is the case.
You can get a Federal Fuel permit- you will want to check to see what the State laws are first. (some States don’t allow it- some states don’t even allow stills at all)
I personally have a fuel permit, keep my logs up to date, and run all my lawn equipment on the fuel I make- I don’t live in Oklahoma so I can’t comment on that. I have yet to have a visit from anyone at the TTB- I send my logs in at the end of the year and that is the only interaction I have had with them.
I think the majority of folks fly under the radar