Carlostrece
$100 Site Donor 2025
This was an accidental post. Please disregard.
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I got my pair of Filter Magnets installed today.
- Thread starter Carlostrece
- Start date
This raises an interesting comparison. Bypass v. Magnet.
Magnet should catch undissolved ferrous debris of a certain size range (?u) and above that comes near enough to the magnet.
A bypass filter should catch ALL debris, 2-3um and larger IF the lubricant passes through the filter. Again, does this make sense for the average passenger car owned 6-8 years? Probably not.
Magnets are cool and great and - yes I am opposed to some lousy magnet that loses flux at 250°F stuck in a filter center tube and may heaven forbid move (yes these are sold!), or a weak magnet on the outside of a steel can (yes these are sold as well) - but otherwise yes, I like GOOD magnets! Especially in a new engine.
Magnet should catch undissolved ferrous debris of a certain size range (?u) and above that comes near enough to the magnet.
A bypass filter should catch ALL debris, 2-3um and larger IF the lubricant passes through the filter. Again, does this make sense for the average passenger car owned 6-8 years? Probably not.
Magnets are cool and great and - yes I am opposed to some lousy magnet that loses flux at 250°F stuck in a filter center tube and may heaven forbid move (yes these are sold!), or a weak magnet on the outside of a steel can (yes these are sold as well) - but otherwise yes, I like GOOD magnets! Especially in a new engine.
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Carlostrece
$100 Site Donor 2025
I agree that bypass filters are the best, if you can afford it and justify the expense. My 2 Filtermag only cost me $112 with free shipping. I didn't want to spend more.
If ignore the higher cost, then I agree with your valid points about why bypass filtration is the best.
However, Filtermag (or other good magnets) are much lower cost and I think they provide some benefits.
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My only question is about "undissolved" ferrous debris. Does the rest actually "dissolve" in the oil?
Just razzin' ya Pablo. 
Kinda sorta, as in the the particles small enough for most equipment used for UOAs to detect. How much is actually in classical solution, tiny.My only question is about "undissolved" ferrous debris. Does the rest actually "dissolve" in the oil?
All that ferrous wear debris is suspended in the oil as it's worn off the moving parts. I don't think any of it dissolves (as in the technical meaning) in the oil and becomes smaller. I'd say most of it is 5u and smaller, so that should be detectable in a standard Blackstone type UOA. There certainly could also be some of that ferrous debris between 5u and 20u. Most of the ferrous debris a magnet catches is the stuff the filters can't catch well ... especially if the filter is lower efficiency.
Agree.
Why I hedged, is chelation. Some Fe, Cu, other metals can be chelated by a few select additives and even some esters. Technically these atoms/ions would be in the (oil) solution. There has been recent discussion on this regarding relatively higher Cu in a UOA. Full circle to what is detected in UOA's, how a UOA could have low metal PPM yet metal caught in the filter (very worrisome), or a UOA could have an elevated metal, nothing of significance caught by even the best filter (somewhat less worrisome).
And back to magnets, these could serve not only as Fe wear metal catchers as well as diagnostic tools.
Re: bold sentence. Yes, I've commented a few times in various threads that a standard UOA can only see debris 5u and lower - like looking through a drinking straw and trying to get a total view of the world. Many times people will see a lot of metallic debris in the oil filter ... may not all be ferrous though. But then they will say the UOA still "looks pretty good" ... might be a slight uptick in wear metals but nothing that might raise a red flag. Since the UOA can only see 5u and less, it takes a large wear event to make the wear metals on a UOA to get into red flag territory.
If someone was doing a UOA and tracking all the UOA data in terms of ppm/1000 miles, they might be able to see if an issue is starting to happen better than is they just do a random UOA now an then. If a UOA had elevated wear levels, but nothing was really seen in the filter, then it's not "catastrophic" type of wear, but most likely just a lot more normal wear, possibly due to using too low oil viscosity for the use conditions. In other words, just a lot more normal rubbing wear because the oil viscosity and/or the AF/AW levels of the oil simply caused more rubbing wear particulate. In catastrophic wear situations, there is that plus tons of particulate much larger than 5u ... like large enough to easily see in the filter and drain pan.
Yes, I use them as a diagnostic tool too ... mostly after the engine is totally broken in. If the level of captured ferrous debris noticeably changes over the same OCI, then it's a possible issue brewing. I take photos of the drain plugs at every oil change, so I have a record of the debris level as the engine racks up miles. I also have magnetic drain plugs in my motorcycles for that same reason, but with them there's still the transmission in the sump that can wear more (harsh use item) than the engine components, so the magnet is constantly catching transmission wear.
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I use them on both my personal vehicles and my fleet. Why? Because it’s another tool to help ensure nothing’s wrong. I don’t run a UOA on every vehicle at every interval—it’s just not that critical in the grand scheme.
These are inexpensive, and when paired with a drain plug magnet, they’re surprisingly effective at pulling out that slimy, metallic mess from the oil. It’s hard to describe exactly, but I’m sure it’s a mix of camshaft sprocket wear, timing chain wear, and other metallic components shedding over time.
In my opinion, why not take it out? That’s why we’re here, right?
These are inexpensive, and when paired with a drain plug magnet, they’re surprisingly effective at pulling out that slimy, metallic mess from the oil. It’s hard to describe exactly, but I’m sure it’s a mix of camshaft sprocket wear, timing chain wear, and other metallic components shedding over time.
In my opinion, why not take it out? That’s why we’re here, right?
Did someone suggest anyone would get something for nothing?
SAE 881825 discusses the correlation between particle size and wear and concluded (if I recall) particles between 2 and 22 microns generated the most wear. Norias life extension tables are an interesting read, as is the McPherson info.
Given full flow filters become markedly less effective below 20 a magnet becomes the prime removal tool as they get progressively smaller.
Small particles that pass through tend to multiply at high rates so getting them out quickly breaks the chain.
A bypass can also do much of that work albeit with more plumbing, chances for leakage, and an additional maintenance point and cycle.
A drain plug magnet will often catch larger chunks a bypass will never see giving you a chance to inspect material before it gets reworked through the engine.
Maybe you dump the oil twice as often - what's the actual cost of that over time?
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