The 2020 rate for employee use of a personal vehicle is 57.5 cents per mile.
Each year, the IRS releases mileage reimbursement rates for the coming year. This is the rate that is commonly used by employers to reimburse employees who use their personal cars for business purposes. If an employer reimburses at a higher rate, the difference is taxable income to the employee. The “charity” rate is meant to cover marginal costs (gasoline, minor maintenance), while the business rate is meant to cover all costs (gasoline, maintenance, insurance, excise taxes, vehicle ownership, etc.) Note that the IRS sets the business and medical/moving rates, while the charity rate is determined by Congress.
The rates for each year can be located on the IRS website, here.