I paid eight hundred dollars for a brake job that I could have done myself for about a hundred and fifty. The mechanic was honest — he showed me the worn pads, the scored rotors, and explained that if I had checked the pads six months earlier and replaced them before they wore down to metal, the rotors would have been fine.

That was an expensive lesson in preventive maintenance. The car equivalent of waiting until you have a cavity instead of brushing your teeth.

Check Your Oil Monthly

Pop the hood. Pull the dipstick. Wipe it clean with a paper towel. Push it all the way back in, pull it out again, and read the level. It should be between the two marks. If it is low, add half a quart at a time and recheck.

Running a quart low does not trigger a warning light on most cars. But it reduces oil pressure at highway speeds, which accelerates engine wear. A quart of oil costs six dollars. An engine rebuild costs four thousand. Check the oil every month. Set a phone reminder.

Tire Pressure Saves Tires and Gas

Underinflated tires wear out the edges of the tread and increase rolling resistance, which lowers your gas mileage. Check the pressure once a month with a gauge — the correct PSI is printed on a sticker in the driver’s door jamb, not on the tire sidewall. The sidewall number is the maximum pressure, not the recommended one.

Gas station air pumps cost a dollar or are free. A set of new tires costs six hundred. A tire gauge costs three dollars. The math is not complicated.

Learn to Spot Worn Brakes

Look through the spokes of your wheel at the brake pad — you can usually see the pad thickness without taking the wheel off. If the friction material is thinner than a quarter, you need new pads soon. Most pads have a wear indicator — a small metal tab that scrapes the rotor and makes a high-pitched squeal when the pads are low. That sound means “replace me now, not next month.”

If you hear grinding, the pads are gone and you are metal-on-metal. That is the eight-hundred-dollar mistake I made.

The Air Filter Costs Twelve Dollars

Your engine air filter and cabin air filter are both accessible without tools in most cars. Pop them out, hold them up to a light — if you cannot see light through the filter, replace it. A clogged engine air filter reduces fuel efficiency. A clogged cabin filter makes your AC work harder and your car smell musty.

Mechanics charge forty to sixty dollars to change these. You can do both in under five minutes for about twenty dollars total.