Deducting Actual Cost. Deducting the actual cost of the gasoline you use is called the actual expense method of deduction. Using this method, you deduct the actual cost of the gasoline you use for business purposes only. You also can deduct maintenance expenses, such as routine oil changes. If you use the vehicle for both business and personal use, you must calculate the percent of time the vehicle is used for business and deduct only that percent of gasoline from your taxes.