yes and all other work related expenses you incur as an IC for Postmates. As I understand it,just like Uber drivers, its your vehicle. if so you can use the standard mileage rate or even actual expenses for the vehicle. no matter which, you must keep records as to business mileage and total mileage. standard mileage rate is 54.5 cents per business mile. if you use actual expenses they're prorated based on business mileage to total mileage. you need to report on schedule C, the income and related expenses
you can not just write off all your gas you put in the vehicle.