Reading an oil filter means eyeballing the filter media to see what has been captured by it. There are really just two critical steps here: how to cut the darn things open and what to look for once you get inside.
The cutting part—as usual—turns out to mean owning a special tool. What you cannot do is whip out the old hacksaw, as that just makes metal shavings—not to mention a zillion jagged edges that introduce your blood to the oil analysis dance. A wheel cutter (think of the round wheel in a can opener) is the need, and so multiple oil filter cutting tools are available from the usual suspects (Aircraft Spruce, Chief’s, various aviation tool companies, etc.).
A bench vice is handy to hold the filter while you cut it open, and sneaking up the pressure on each turn of the cutter works far better than going Conan with one mighty, can-crushing twist of the tool. Cut the base off the old filter and throw it away before it cuts you. Drain what residual oil you can from the now-open filter housing and pull out the paper filter element.
The paper element is wound around a central spindle, so now you need to cut the element away from the spindle at its two metal ends. A sharp knife is your best friend here (give it a good wiping before returning it to the kitchen drawer). Pull the pleated paper away to end up with a long, dripping mess looking like Jack the Ripper got ahold of a concertina.
Given a reasonably fresh engine, simply eyeballing between the pleats is sufficient. You are looking for small metal slivers or faceted chunkies. A small magnet will tell if they are ferrous or aluminum. Ferrous in any noticeable quantity is not good (they are from the crankshaft, con rods, piston pin, and valve train parts), while aluminum can be piston skirt or crumbly case bits finally shaken loose. Don’t worry about the odd bit of metal; incredibly, that is normal as the engine shakes or wears loose casting flash or some proud bit.
If you get dark crumbs that crush under a bit of pressure, don’t worry at all. Those are carbon bits, proto-diamonds made from burning hydrocarbons (gas and oil). You might want to consider oil consumption and general engine wear if you are getting teaspoons of the stuff.
Many times you will get nothing at all, a sign of a good engine.
For a more thorough reading of the filter entrails, put some mineral spirits in a (clean!) bread pan and swish the filter element in the spirits. Then examine the element and the grit in the bread pan. Straining the mineral oil through plain white paper towels will uncover even more stuff. But remember, the more you look, the more you will find.
As a newbie it is difficult to know what you are looking at, so have a friendly old hand help with cutting and eyeballing the filter.
Lycoming SB480F is a great guide to interpreting what you find in the filter pleats.
Blackstone Laboratories, amongst others, will analyse your engine oil and the metal bits that come out of your filter. There are other firms. Blackstone is what is recommended by Savvy Aviation. Mike Busch, of Savvy Aviation, has some Audible and print books on Amazon. Some people think he’s a bit too much into marketing himself but I thought that the books were excellent.
I think that Mike only says that Blackstone is the outfit that he uses, not necessarily recommending them over others. That said, they do appear to provide a more comprehensive analysis than AOA.
Either way, oil analysis isn’t a substitute for checking the filter or oil screen. Not that you said that but it might be inferred that way by some.
Apparently Lycoming engines also have a pre filter that picks up metal bits. You can send off the oil and filter products for analysis.
A couple of refinements to the technique described. Lay the filter element out on an old cookie sheet and walk away for a few days. Gravity will do its thing and you’ll have a much less saturated medium to check for shavings. Then, move a magnet under the paper pleats; magnetic bits, which are the ones you should principally be worried about, will dance as the magnet passes by.
On my EAB, I went with a K&P Engineering all-metal filter and with a Rube Goldberg washing setup capture all the debris on a clean, white 35 micron nylon mesh for detailed inspection.
Yup, I run the solvent solution through a white coffee filter and sometimes I find a few tiny carbon flakes that have become magnetized, too. Or, perhaps, the tiny carbon flakes have some tinier metal pieces in them. Not sure which (or both?) but any metal that small is not going to matter to me.
It is never a great thing to find ferrous material in the oil filter. However, on fresh engines there often will be some bits found. Even factory new. We’d love to think that these beasts are made with sub micron precision, but that’s just not the case. The surface finish of steel parts may be world class, but the fit is not. This is one reason the very best engine builders get such good results. They understand the stack of tolerances, whether a new Lycoming cylinder gets rejected (yes we replaced 6 cylinders with 90 hours TT due to sloppy machining and very poor dimensional tolerances). My point, watch the ferrous material levels carefully. But don’t immediately panic if stuff sticks to the magnet, change the oil regularly, choose good products and monitor carefully. Think old school Briggs and Stratton where the first few oil changes had glitter, but the stupid thing lasted 30 years with good maintenance.
I’ve often said, if I was going to fly around the world with a single engine, it would be with a Briggs and Stratton……if they had one big enough.