[adrianN]

Mister Money Mustache estimates "very cheap" driving costs to be around 17 cents per mile:

https://www.mrmoneymustache.com/2011/10/06/the-true-cost-of-...

Now, I will admit that it is possible to bring your cost per mile down somewhat. That’s one of my own specialties, which is why I still keep a car of my own around for affordable family roadtrips. If you buy the right car for $5,000, you might be able to squeeze 100,000 miles out of it with no major repairs. In this case the car depreciation is 5 cents per mile.

Gas, at $3.50 per 35 miles (assuming 35MPG), is 10 cents/mile Tires, at $300 per 50,000 miles are 0.6 cents Oil, at $25 per 5,000 miles is 0.5 cents Miscellaneous things like wipers and occasional maintenance visits: $200 per 20,000 miles = 1 cent

So the ultimate cheap driving in a paid-off economy car still costs at least 17 cents per mile.

[Robotbeat]

It's possible to do even better... I bought a used electric car (Volt) for about $9600. It had about 65k miles. It does about 85% of its miles electric (meaning oil changes and brakes are super rare), so over the next 100,000 miles, we're talking about 14 cents per mile total, roughly.

[bluGill]

Many of the assumptions are different for different cars. For my car it is $3 per 46 miles, or $0.065/mile. Note that 46MPG is actual, EPA would give me 41.