I have two MotorGuard filters that were modified for use with fluid (engine oil, transmission/hydraulic fluid) by an old boy down in Texas by the name of Ralph Woods. They use a roll of toilet paper as the filter medium:
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Once upon a time MotorGuard actually marketed these for engine oil, then for whatever reason (company changed hands, taken over by the kids, etc.) they quit doing it.
They are great as a
bypass - not primary - oil filter.
At one point I had them on my Dodge Sprinter (Mercedes 5 cylinder diesel) - one on the engine and one on the transmission:
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Normally, the Sprinter would go around 12K to 15K miles, using just the stock OEM oil filter and the OEM oil change sensor (which I believe measures the di-electric component of the oil, to determine when the oil needs to be changed)
I think the longest I went, doing regular filter changes on the bypass filter and topping off ... along with used oil analysis from Blackstone, before draining the sump and changing out the oil, was somewhere between 60K and 75K miles. And the oil in the sump was still actually good at that point ... I could have gone longer.
The van currently has over 435K miles on it, original engine.
BTW, these type of filters are still available under another brand name, which I don't recall offhand.