Tax rates on motor fuel by type and state from the U.S. Department of Transportation's Federal Highway Administrations' Monthly Motor Fuel Report, available at: https://www.fhwa.dot.gov/policyinformation/motorfuelhwy_trustfund.cfm

All States levy volume taxes on gasoline and diesel fuel. Traditionally, State fuel tax rates could only be changed with legislation, but as of 2021, 10 States have variable rate motor fuel taxes. These taxes are adjusted at specified intervals annually, semi-annually, or quarterly. Adjustments to variable tax rates are announced by State tax agencies shortly before the effective date of the change.

The fuel tax rate is collected annually and therefore the semi-annual and quarterly adjustments are not captured in the data.