The state’s new motor fuel tax of 38 cents a gallon will be tied to the Consumer Price Index effective July 2020.

That means every March, the Illinois Department of Revenue will use federal inflation data from the previous 12 months to set a new tax rate to begin in July.

For example, the recent 12-month average increase in the CPI in the Midwest was 1.8%, which would result in a new gas tax of 38.7 cents, in theory.

The changes mean taxes could account for as much as 91 cents of the price of a gallon of gas in the suburbs, with a little variation depending on the town and county where it is purchased.

Also, the state gas tax now will rise annually starting in 2020, without lawmakers having to vote on the yearly increases.

Under the new law, DuPage, Kane and McHenry counties now are allowed to increase their motor fuel tax from 4 cents to 8 cents a gallon and use the money for highways and roads.

Lake and Will don’t have county gasoline taxes but were similarly authorized to impose a tax of up to 8 cents per gallon. Lake County commissioners will discuss that topic next week.

Another change is that any town in Cook County now can charge a 3-cent local gas tax that would be collected by the Illinois Department of Revenue. Now, only home-rule towns in Illinois can collect a local gas tax, without a state-imposed cap.

To learn about your town’s taxes, go to mytax.illinois.gov.

Cook County’s short-lived penny-an-ounce sweetened-beverage tax showed that a lot of Illinois taxpayers were willing to take their business elsewhere. Cook County officials repealed the “soda tax” after retail sales took a big hit when people shopped in neighboring counties and out of state.