Most "cost of driving" calculators consider fixed costs like total depreciation, taxes, insurance etc.
But I've been trying to calculate the amount of money I save by leaving my car in the driveway and riding my bike all these years.
For example, the car depreciates, but it depreciates less by not driving it. It also still needs periodic maintenance. But it needs less periodic maintenance when I drive it less.
I calculated the depreciation as about 4 cents a mile. I did this by comparing the value of my car with 70,000 miles vs the 100,000 it would have if I'd been driving it to work every day.
Maintenance is a bit more tricky. I bought new tires in 2006. They have about 7000 miles on them. I get the oil changed about once a year. Any idea how to convert that savings into a per-mile figure?