I was prompted to post this after watching a popular car guy on YT (300K subs) cut open used oil filters in his shop after several comments had suggested it. Once the outer skin was removed he looked in the element and between some pleats and basically said nothing to see here, I will never cut open another oil filter again. He should have cut open the filter from the C5 which was rapping badly instead of a DD. He does agree on using oil analysis.
I disagree somewhat, I've been cutting open oil filters for 30 years, mainly on fresh rebuilds through break in, then later at 10-15k miles. SAE 30 initial on flat tappet SBCs and SBFs.
I used a screwdriver and hammer to pop a hole in the skin then used aviation snips to cut it away down to the mounting flange. Use a sharp knife to cut the pleats away from the metal, remove the pleats and spread them flat and examine.
What I've learned: On the first oil filter after rebuild I've found metal flecks, RTV and paint that I would call normal. Safe to say I think I'd know what excessive metal would look like. Cut open 2nd oil filter after 2-3K of recommended oil. Follow up later at 10-15k. Fortunately, I've never found anything excessive but it was worth the look to me. Also use a magnetic drain plug.
Only took 20 minutes start to finish including clean up. Cheap insurance to me. If I had found any excessive metal I'd stop right there.
I've also routinely cut open oil filters on race engines at oil changes. Basic CYA to catch something early.
As oil analysis has become more mainstream now for those who subscribe I still find cutting open oil filters valuable on rebuilds and race engines. Maybe that 'ran when parked' vehicle you dragged home but don't know why it was parked.
What does GRM think?
Cut a few open at the track if engine did something weird. Had a rock knock a hole in the filter one time and didn't know until the light came on and the gauge was buried. Put a new filter on, refilled the oil and it didn't make any unusual noise so we raced it. Then cut the filter open to check for damage. Didn't see anything so we didn't pull the engine. Ran fine for the rest of the season. Then freshened it.
It can be helpfull but by the time you see stuff in the filter it is usually rebuild time. It costs nothing and is a tool that can help diagnose things.
Oil analysts will detect things sooner and may allow for "just a bearing replacement" instead of a complete rebuild. Again another tool/test you have that is relatively cheep.
I've done it to verify that the filter I was using was indeed the OEM filter at 1/4 the cost of OEM. I never saw anything I didn't expect to see in there
I've never worried enough to take the time to cut one. I figure by that point the rattle will let me know something bad is happening.
I do it on all race engines after the initial Dyno run. My dry sump engines run Oberg filters to make inspecting the filter even easier.
For those who do oil analysis, where do you have it done? Thirty years ago, I received some mailers and test tubes that I could send samples in for testing. A few weeks later, a printout would come in the mail. I think I did it twice. Nothing of note in a fairly new daily driver. I haven't thought about it since.
How does it work nowadays?
All the time. It's why I prefer cartridge filters to spin-on filters.
Here's my S40 from when I got it in 2014. Drained the oil, installed a new filter and four quarts of ATF, removed oil filter after 100 miles and cut it open:
I went through several filters like this before the ATF stopped pulling sludge from the inside of the engine, then I went back to normal engine oil.
Here's a FB25 oil filter that we suspected had internal engine problems.
Lots of big flakes, nothing magnetic. There was one (1) bad rod bearing.
