Gasoline tax is complicated.
Hmmm... I never looked into how fuel tax varies across state lines. Always thought CA has the highest, but it is only #2.
Note that there are fed tax, then state tax, and also sales taxes in some states. And then, there are gross receipts taxes, oil inspection fees, county and local taxes, underground storage tank fees and other miscellaneous environmental fees, according to API.org. I have read that gas tax is a complicated thing, and the above explains it.
The numbers below are the averages in each state, according to API.org (American Petroleum Institute).
As of 4/1/2019, the honor goes to PA at $0.771/gal, followed by CA at $0.7358, WA at $0.678, HI at $0.6516, NY at $0.6375, etc...
IL was at $0.5527 on 4/1/2019, becoming $0.7427 after the 19c increase if nothing else changes, making it surpass CA.
FL on the other hand is at $0.6039, according to the same source. So, sorry Amethyst, but Illinois residents have the right to complain.
And by the way, AZ is at $0.3740, and TX at $0.3840.
See:
https://www.api.org/~/media/Files/Statistics/State-Motor-Fuel-Taxes-Report-April-19.pdf.