How often should I really change my engine oil?

Follow the interval in your owner manual rather than a general rule. Modern engines with synthetic oil commonly specify intervals far longer than the old advice of every few thousand miles, and that older figure persists largely because it suited businesses selling oil changes.

Many cars now calculate the interval themselves, monitoring engine temperature, load, trip length and revolutions rather than distance alone. Where a car has such a system, trusting it is generally better than a fixed schedule, because it accounts for how you actually drive.

The distinction that matters most is between normal and severe service, and most manuals define both. Severe service is not extreme driving; it typically covers frequent short trips, extensive idling, towing, dusty conditions and very cold or very hot climates. Short trips in particular are harder on oil than long ones, because the engine never reaches full temperature and moisture and fuel dilution accumulate rather than evaporating.

A great many drivers who assume they are in the normal category are in fact in the severe one, which is worth checking.

Time matters independently of distance. Oil degrades through oxidation and contamination whether or not the car moves, so a vehicle driven very little still needs changing on the time-based interval, usually annually.

Using the specified oil grade and specification is more important than changing more often with the wrong one. Modern engines with variable valve timing and turbochargers have tight tolerances and rely on specific oil properties, and the correct specification is printed in the manual.

If you are unsure whether an interval is being met, an oil analysis is inexpensive and gives a direct answer rather than an estimate.