The point is that 50 cents an hour is not an accurate representation of the cost of continuously operating a car for an hour. The IRS allows something near that

The point is that 50 cents an hour is not an accurate representation of the cost of continuously operating a car for an hour. The IRS allows something near that per mile as a standard mileage rate. If the car is driving more than a mile per hour on average, it's significantly exceeding 50 cents/hour.