It's important to not use the IRS Mileage Rate to calculate real cost. (The linked study does not.) The IRS rate is designed for the worst case scenario for the purpose of tax filing (coz you don't want to penalize someone who has to drive a F-150 in a high-gas-price state in a year where gas price spikes to $5/gallon). Even if we don't consider the fact that the cost of vehicle depreciation, maintenance and insuranc…
But all of these costs go up if you drive more miles. Your vehicle depreciates more if you put more miles on it (but not if it's parked in your garage), you need more frequent oil and tire changes, and your insurance rates go up because you're more likely to make a claim the more miles you drive annually. And rideshare insurance is more expensive.