If you’ve ever looked at a maintenance schedule on when to service your car, you’ll notice it includes two completely different choices for service intervals: mileage and time. You’ll see something like “transmission service — 24,000 miles or two years.”

But which is it? Should you base your maintenance schedule on mileage driven or the time elapsed since the last service? Does it matter or should you just pick one?

Scheduled Car Maintenance Matters

Scheduled Car Maintenance - Cottman Man - Cottman Transmission and Total Auto Care

The simple answer is, whichever provides a shorter interval. In the example shown, if two years goes by and you haven’t driven 24,000 miles, use time as your basis. If you hit 24,000 miles in less than two years, use mileage for your service interval.

The reason manufacturers use two seemingly unrelated intervals is simple: Some people drive more than others. But not driving your car takes its toll on the moving parts, too. Acids build up and moisture condenses as your car sits. Driving burns those contaminants away. If you don’t drive enough, the only way to eliminate them is by draining out the old oil and replacing it with fresh oil.

Help Choosing Mileage Or Date Maintenance

If you aren’t sure how to work out your maintenance schedule or when to service your car based on your driving characteristics, your local Cottman center will be happy to help. Stop by and let them know about your driving habits: what type of driving you do and how many miles you drive each month or each year. They’ll show you how to calculate the exact right schedule for your car, and they’ll be able to take care of those maintenance items for you.

Mileage or time… as a rule, choose whichever comes first.