Oil Change Interval Calculator
The 3,000 mile rule is decades out of date, and so is ignoring severe service. Work out an interval from the oil you run and how you actually drive.
Your oil and driving
- Your manufacturer's interval and oil specification always win. This estimates, it does not override.
- If the vehicle has an oil life monitor, use it. It watches real operating conditions rather than assumptions.
- Oil degrades with time as well as mileage. A low mileage car still needs changes on a calendar.
Where 3,000 miles came from
It came from conventional oil in engines with carburettors, looser tolerances and no emissions controls to speak of. That oil sheared down and oxidised quickly, and 3,000 miles was reasonable.
Modern full synthetic in a modern engine is a completely different product. Manufacturers routinely specify 7,500 to 10,000 miles, and some European long life specifications go beyond 15,000. Changing good synthetic every 3,000 miles wastes money and oil.
Severe service is more common than normal
Read the definition in most owner's manuals and you will find that short trips, stop and go traffic, towing, dusty roads, extended idling and extreme temperatures all count. Most people driving to work in a city meet the definition.
Short trips are the worst of them by a distance. Oil needs to reach full temperature to boil off the fuel and water that condense into it during warm-up. A car that only ever does ten minute trips accumulates both, and that is what turns oil into sludge.
Time counts too
Oil oxidises whether or not the car moves, and additives deplete on a calendar. A car doing 4,000 miles a year on full synthetic still wants a change annually rather than every two and a half years.
Frequently asked questions
How often should I really change my oil?
For full synthetic in normal service, 7,500 to 10,000 miles or annually. Conventional oil wants 5,000 or six months. Severe service, which includes short trips and towing, cuts all of those substantially. Follow your manufacturer's figure where one exists.
Is the 3,000 mile rule still valid?
Not for modern engines running synthetic oil. It survives because it suited quick lube business models rather than because the engineering supports it. Conventional oil in an older engine doing hard work is a different case, and there 3,000 to 5,000 can be right.
Does short trip driving really matter that much?
More than anything else on this list. Oil that never reaches full temperature keeps the fuel and water that condensed during warm-up, and that mixture forms acids and sludge. A car that only does short trips should be on roughly half the normal interval.
Can I trust my car's oil life monitor?
Generally yes, and more than a fixed mileage figure. Modern monitors track engine temperature, load, trip length and rpm rather than just counting miles, so they respond to how you actually drive. Change the oil when it says to, and still change it annually if the mileage never gets there.
Everything on this page is an estimate worked out from the numbers you entered and typical figures for the conditions you picked. Your vehicle, your parts and your conditions will differ. Check anything you intend to act on against the manufacturer's specification, the service manual, or a qualified technician. Verifying the result before relying on it is up to you.