Toilet Paper Oil Filter (was Re: [Farmall] Super M Oil Filter)

[George Willer]

Steve,

Your comments remind me of a discussion a couple of us had just yesterday. 
It was about furnace filters, but the same rules apply.  As the filtering 
element does its' job of trapping foreign matter its' efficiency goes up... 
meaning it will trap ever increasingly small particles.  As the efficiency 
goes up the flow rate goes down, until the efficiency approaches 100%.  At 
that point there is very nearly no flow at all!

I would expect a TP filter to reach that point fairly quickly.

You've been conspicuously absent from the BS sessions at Portland for far 
too long! :-(

George Willer

Subject: Toilet Paper Oil Filter (was Re: [Farmall] Super M Oil Filter)


>I give Ed a lot of credit for his careful handling of the commercial 
>disclaimers.
>
> Personally, having only ever heard of the TP oil filter in the notoriously 
> chintzy JC Whitney catalog of 25-ish years ago, I had a generally negative 
> default opinion from the outset.
>
> To my surprise, a Google search turned up military specification documents 
> referencing bypass oil filtration and toilet paper cartridges.  Maybe 
> there *is* some legitimacy here...?
>
> Correct me if I'm wrong:  I understand that the factory "full-flow" type 
> filter is designed for high flow and low pressure drop, and therefore has 
> relatively large pores in the filtration media.  The TP filter does not 
> replace the factory filter but rather is run in addition to the factory 
> filter.  The TP filter has effectively very small pores and the downside 
> is a much higher pressure drop and reduced flow rate.  Therefore, full 
> flow cannot be run through the TP filter or the engine would starve for 
> oil.  Instead, a fraction of the total oil flow is bypassed and run thru 
> the TP filter where it is cleaned more thoroughly because the filter media 
> has much smaller pores and traps smaller particulate.  This oil mixes back 
> with the bulk of the oil, but over time, an averaging effect takes place 
> and all of the oil at some point passes thru the TP filter.  OK so far?
>
> Questions that arise in my mind:
>
> - A guiding principle in engineering is that everything always takes the 
> path of least resistance.  Since the TP filter is such a heavy 
> restriction, exactly what is the relative flow rate between the oil 
> passing thru the TP filter vs the amount that bypasses?  I would think the 
> flow differences would be quite large, and effectively a tiny fraction of 
> oil is actually being filtered in the TP filter at any given time.
>
> - Claims are made that oil never needs to be changed.  This concerns me. 
> There is far more happening in the oil than merely loading up with 
> microscopic particulate.  For one thing, acids tend to form, due to 
> combustion byproducts blowing past the rings.  These acids probably won't 
> touch cast iron, but I'd be quite concerned about acidity (over time) 
> damaging bearing shells.  For another thing, oil does in fact "wear out". 
> Long-chain hydrocarbons break down over time, resulting in what the TV ads 
> call "viscosity breakdown".
>
> - Laboratory oil analysis is quite common these days, and readily 
> available. Has an oil sample ever been tested from a vehicle run for an 
> extended period of time on the TP filter with NO oil changes?  Aside from 
> basic data indicating the condition of the used oil from a lubrication 
> standpoint, this would also turn up evidence of metals such as copper that 
> are being broken down by acids, not to mention stray substances arising 
> from a breakdown of the TP itself.
>
> I'm not criticising Ed.  I am genuinely curious.
>
>
> Best regards and Happy Holidays to all,
> Steve O.
> Sterling, CT