Earlier quoted context omitted.
The term "engineer" is definitely protected in Texas, and I think some other states.
Someone ought to tell whoever put all these job listings up (including in Houston): https://www.rigzone.com/a-mud-engineer-jobs/ ADDED: TIL apparently Texas is indeed exceptionally restrictive (in theory) about the use of the term "engineer." [1] I'd be pretty certain this is widely ignored in practice. Leave the oil business aside, I'm guessing that tech companies in Texas probably advertise engineering positions no…
Go look into the actual law, you legally can't call yourself an engineer in Texas without a PE, or a couple tiny carveouts (on the order of you work at NASA, and NASA calls you an engineer)