[Arch-TK]

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).

Anyone who actually drives their car regularly will be doing an oil change at least twice a year. If an oil change takes more than 30 minutes of actual labour time of an inexperienced mechanic, it's going to be a serious financial burden which will likely outweigh any 2mpg improvement.

[bluGill]

> 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.

[Arch-TK]

> 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.

[bluGill]

Cars are fairly easy to service, and and so get shorter oil change intervals. industrial engines often get bigger filters. A thermoking refrigerator has a massive filter for a tiny 2 liter engine (at least the one unit I've seen - which was at least 30 years old, I don't know what the latest do)

[bluGill]

Follow the manufacture recomendations. it sounded like a recomendation to replace more often. Maybe we are in agreement?

filter test can be inferred from flow rate and oil analisys. Destructive testing is best if you must know - but also not helpful.

[its_ethan]

I'm just gonna copy and paste a response to another similar comment: The point that I am making (obviously, I think) is that tradeoffs exist, even if you don't think the right decision was made, your full view into the trade space is likely incomplete, or prioritizes something different than the engineers.

Putting some random number of hypothetical mpg improvement was clearly a mistake, but I assumed people here would be able to get the point I was trying to make, instead of getting riled up about the relationship (or lack thereof) of oil filters and fuel efficiency.

[Arch-TK]

You can also read my reply in my other comment.

But to keep it concise: The core problem is that you are stating a truism in response to a famous counter-example to specifically that truism. The other problem being that you are stating a truism which everyone else is already familiar with.

[its_ethan]

Given how many people have seemingly jumped on misinterpreting the truism as me making some claim of a specific fuel efficiency improvement, I'd disagree with people being already familiar with it.

To be concise as well: it's been duly noted by me that contributing to a conversation by attempting to bring in nuance is not always well received when you make up a hypothetical for a topic people are very touchy about.

[quickthrowman]

> You should be replacing them every 6 months / 6k miles, or 12 months / 12k miles depending on your risk tolerance

You should be replacing your oil filters based on the manufacturer’s service schedule, there’s no rule of thumb. Look at the service manual, my car has the filter change scheduled every 10,000 miles.