Cost and Capability, Not Car Loans
Vehicle math splits into two kinds of questions. One is what a drive costs: fuel burned, miles covered, money spent at the pump, and how it compares against flying or taking two cars. The other is what the vehicle can do: how much it can tow, what a tire size change does to the speedometer, how far a tank really goes. Both are arithmetic, and both are things people get wrong at the kitchen table before a trip.
This category deliberately leaves out auto loans, leases and depreciation schedules. Those are financial products with their own rules, and they belong with a lender rather than a calculator. What is here is the tool side of owning a car: start with the fuel cost calculator before a road trip, and check back as the rest of the mileage and towing tools come online.