Ask HN: What Is the Absolute Cheapest Car to Own and Drive?

Let's suppose I wanted to buy a car. But I'm brand agnostic and mileage agnostic. That is, I'm willing to buy any car regardless of its make and model or how old it is. Now, I'd like to buy a car which is going to cost me the absolute least money of any car new or used, that I can buy, over its lifetime, including repairs. How would I determine which car that would be? Now, in thinking about this, I see quite a lot of problems, which include, but are not limited to: -Fluctuations in price of the used car market -How to calculate the cost of future repairs -What the cost of gas is and that related to how many miles will it be used in an average week -Tax deductions, if any -What the future cost of gas is projected to be -How much insurance would cost (sub-problem, what would the cost of the cheapest insurance be?) And of course, how to monitor all of the cars from all of the vendors/markets for a given area. Now, I don't have an answer. It seems like a problem involving multiple domains, requiring huge amounts of statistical data, recurrence relations, data from multiple sources, etc. But... in thinking about it, I think this would shine as an interview question for my future company (assuming future applicants don't read Hacker News). But, what does the HN community think? What additional things need to be accounted for if I wanted to find and buy the absolute cheapest car?