Well, it took them longer than usual but the IRS has updated the rates used to calculate your mileage deductions. As a reminder, there are different rates depending on what type of driving you are doing.
The business mileage rate is applicable for business purposes. This would be for activities such as your sole proprietorship (Schedule C) or your farm (Schedule F).
The main thing to remember for 2018 and future years is that you can’t use this mileage rate for unreimbursed employee expenses. These are the expenses that (before 2018) would have been reported on your Schedule A for Itemized Deductions. The Tax Cuts and Jobs Act of 2017 took the unreimbursed employee expenses away so you won’t get this deduction any longer.
You can read the official IRS announcement here: IR-2018-251, December 14, 2018