The principle seems fine (if you don't use something much then the overhead of renting when you do need it is probably worthwhile), but it feels a bit odd apply

The principle seems fine (if you don't use something much then the overhead of renting when you do need it is probably worthwhile), but it feels a bit odd applying it to cars in particular unless you live extremely close to work -- a bit of a moot point with wfh right now -- since you'll be using the car enough that your dominant costs are variable rather than fixed. If 50% of your yearly car ownership costs stem from gas and other variable costs then "paying for the 95%" is a strawman since the variable costs won't decrease by renting a car (and in fact are often many times higher), so you can only reduce your total costs by at most a 2x factor.