Ok, i still have a car, and my wife will sometimes use it. We've filled the tank three times this year.

EDIT: i think it's important to note that when we were both driving, it was often mindless and not planned out. Back then, we'd be filling the tank every 2 weeks at a minimum, so it was extremely expensive (and wasteful) compared to now.

Because we're also on pay-as-you-go insurance, it's dirt cheap.

What I've done over the last year or two is to calculate how much gas and insurance would have cost, had i used a car and not a bike to run errands (i exclude recreational rides or rides specifically because of the bike, like going to pick up parts).

I take the amount and transfer it to a separate bank account. In the last 12 months, it grew to over $400.

That doesn't include anything else we might have saved by not using the car.

Granted, i did invest a bit into equipment to help replace my car, like panniers and bike trailers. But they'll last an exceptionally long time, so they'll eventually pay for themselves.

That's one thing i noticed with car vs bike expenses. Most car expenses are one-and-done. You have nothing to show for it.

Bike expenses, for me, are mostly things that enhance the experience and utility of cycling.

If my wife was able to bike as much as I do, I'd honestly probably not want to own another car and invest in two ebikes instead.

Good luck with everything!