How often to change the oil?

The eternal question every car owner has asked themselves, or a mechanic at the garage, at least once in their life. On one hand, it's clear that the more often you change the oil, the better. On the other hand, good engine oil is never cheap, and changing the oil takes a fair amount of time. So where's the compromise, and how do you correctly figure out which service interval is right for your car?

You won't find a single definitive answer on this site about how long the service interval should be — 8, 10, 15 or 20 thousand km — that's up to you; we'll only try to point out which factors should guide that decision.

That's right — there is no one-size-fits-all answer to "how often should I change the oil?" in nature. Still less is there a universal answer for every car and every owner; it's all individual. There is only the change interval recommended by the manufacturer, found in the service book. On top of that, there are outside factors (not accounted for by the automaker) that shorten the useful life of the oil sitting in your engine. Beyond that, it all comes down to how badly you want to keep your engine in good working order...

So the correct logic for judging the optimal oil-change frequency for your engine is fairly simple:

1. Look at the manufacturer's recommendation for the recommended service interval.

2. Work out which factors in your car's life, besides mileage and time, bring forward the moment when it's time to change the oil.

3. Come up with your own individual coefficient (based on point 2) by which you'll shorten the manufacturer's recommended service interval.

4. Change the oil based on all of the above, and stop worrying about it beyond that :).

Why shorten anything at all? When a car manufacturer works out the oil change interval, it usually assumes “European” operating conditions: clean roads, good fuel, a sensible mix of city and motorway driving. And some carmakers go further and treat the length of the service interval as a marketing point, writing into the service book the longest possible interval with which the engine is guaranteed to survive until the end of the warranty.

If you need a starting point, here it is: in hard conditions (city traffic jams, short trips, dusty roads, poor fuel) the change interval should be noticeably shorter than the one written in the service book. And the figure in the book is the maximum, not the norm, and it's not worth stretching it.