"If you’re in college and just drive for Uber on occasional weekends, it doesn’t make sense to include all of the fixed costs of the vehicle in your profit calculations."
But it does make sense to prorate the portion of those fixed costs associated with the Uber use. Failure to do so is a major business mistake, since you will have to replace the vehicle, etc., sooner than you would otherwise.
Which means something like a conservative 53¢ per mile.
You have to prorate some portion of the fixed costs, but it seems like the 53 cent figure is assuming that the entire lifetime of the vehicle is used for business.
53¢ is the US government's ("We're here to help you!") estimate of the total cost of an average vehicle divided by the lifetime of the vehicle as measured in miles.
If your vehicle's lifetime is 200,000 miles, and 10% of that is assignable to Uber, that is 20,000 miles or $10,600, which is 10% of the estimated lifetime cost of $106,000.
If you try to break that up into different "buckets" ("I need a car anyway, so I shouldn't apply the fixed costs to my Uber income"), you end up with a car that effectively only lasts 180,000 miles and therefore your fixed costs for the car for personal use are artificially higher. It is the same thing as if you had decided "I would just burn that gas anyway" and didn't count fuel costs against your Uber income.
But it does make sense to prorate the portion of those fixed costs associated with the Uber use. Failure to do so is a major business mistake, since you will have to replace the vehicle, etc., sooner than you would otherwise.
Which means something like a conservative 53¢ per mile.