alt Hacker News> We don't have magic oil filters which last even 22k miles. You should be replacing them every 6 months / 6k miles, or 12 months / 12k miles depending on your risk tolerance (some people suggest even half my short interval).
We do - they are just a lot bigger.
You should replace the oil filter when it is no longer filtering. Replacing it early is a pure waste of money. Unfortunately the tests of do you need to change the oil filter is more expensive than just replacing the filter so just replace it before it can possibly be clogged is the right answer. Generally the manufactures recommendations are correct and you should follow what they say unless you have lab results that say otherwise.
> We do - they are just a lot bigger.
Yeah, of course, but I am not aware of any regular car which comes stock with such filters.
The point was really that lasting 22k miles longer than stock would be an unrealistic improvement for a filter for a normal car.
> You should replace the oil filter when it is no longer filtering.
I was specifically referring to manufacturer recommendations. Of course they're conservative, they also have to account for engine wear.
And yes, you are right that ideally you'd test. Although testing the filter from what I've seen is destructive, and there's a nontrivial turnaround time.
I'd disagree that following manufacturer recommendations is a waste of money though. As you say, testing is _more_ expensive. Engine damage is even more expensive. Replacing the filter on schedule is the economical choice.
It might be strictly a waste of resources, but that's a separate concern.