I haven't had a car payment since 1989; every car I've owned since then was an outright cash purchase -- yep, that's right, cheap old crap.... a total of 7 old cars, none over $900. Insurance was always PL/PD, license plates were always the state minimum. Gas mileage was never over 17mpg until the last one -- that baby, the hatchback, got 27mpg even the way I drove it!

That was the figure I used to determine my savings after going 'car-lite'; my sister's family lives with me, they have 2 cars, but I drive maybe 2x/year. Other than grocery shopping for the house, all their driving is for them. They pay those costs, doesn't cost me a dime.

I know the mileages of my various commute routes and errands, and I can well estimate my 'fun rides', as well. So my annual mileage, even without a bike computer, is a pretty accurate estimation.

Recently, I figured up the miles I put on the frame I'm about to replace (cracked); baby rolled 15K in 4+ years. So, at 27mpg, and gas between $3 & $3.50 a gallon over that time, my math says this bike paid for itself almost a year and a half ago, just in gasoline costs saved! Maintenance -- oil changes, tuneups, brake jobs, etc. -- pretty much balances out, what with multiple sets of tires, chains, and gears, and two sets of wheels. So, I saved 100% on insurance, and about 35-40% on gas!

Basically, I could buy a new $2K bike every 3 years and break even! If it lasts longer, I save (and they pretty much do)!