Beyond the recognized "Formulas" such as Formula No. 40-B, there are a number of other "flavors" of denaturants, pages of them starting at section 21.91:

https://www.ecfr.gov/current/title-27/chapter-I/subchapter-A...

The only purpose is not to "jeopardize the revenue."

In that respect, regardless of the rate being levied, the result on behavior was intended to be very strict and immediate.