Car Due

How it works

Miles. We guess 250 miles a week until you tell us more. One odometer reading plus your model year gives your lifetime pace. Two readings three weeks apart give your real pace. Any service you log with miles counts as a reading. Between readings we draw a straight line; after the last one we extend it at your pace.

Oil, rotation, balance. Each is due at a mileage or an age, whichever comes first. A car that sits still still needs oil. Nothing logged yet? We work backward: "last done before this date? Then it's due now."

Tire pressure. We take the pressure each wheel was set to and the morning low that day. Air pressure follows absolute temperature, so a 40 °F drop takes about 4 psi. Healthy tires also seep 1–2 psi a month. We remind you when any wheel looks 3 psi low, when a cold morning in the 16-day forecast will make it so, or a month after the last check, whichever comes first.

Each wheel. Wheels get letters A–D. Log the pressure you found before adding air, and we learn each wheel's own leak rate. A wheel that loses 3 psi a month or more gets flagged as a slow leak, and the flag follows it to its new spot after a rotation. We also count each tire's miles on the front and rear axle.

Rotation patterns. Front-wheel drive: forward cross (fronts straight back, rears cross forward). Rear, all and four-wheel drive: rearward cross. Directional tires: front to back on the same side. Your owner's manual has the final word.

These are estimates. Your owner's manual, your oil-life monitor and a $5 tire gauge beat them. Check pressure in the morning before you drive.