Revisiting the Oil Filter

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Al Zim
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Revisiting the Oil Filter

#1 Post by Al Zim »

Sometime it the not too distant past there was a long discussion about the filtering ability from the factory oil filter. More recently I have been trying to replace the oil filter bolts that we used on engines where the bolt was lost. During last week we decided to see if the filters that were used on the 356 were similar to a USA made product. My experience with old farm equipment that I used suggested that this was a filter similar to the one on my Ford tractor.
After some research one of the parts guys found that the Porsche filter is very similar to the one used on the WWII Jeeps and other military equipment. This prompted us to ascertain the flow through the filter. The determining factor on oil flow through the filter is the size of the hole in the banjo bolt at the base of the inlet line to the filter. This is 1.4 MM in diameter (less than one and one/half millimeters, about the thickness of a new penny). We calculated the flow through this hole with a formulae form Google. Water at 60 PSI will flow 110 Liters per hour. If hot oil flowed as fast as water (probably not) the capacity of the engines oil would be filtered only about 25 times in an hour. Which clearly indicates that the oil filtering system was designed to increase sales not to prolong engine life. It is important to change your oil frequently the Porsche recommended every 3000 miles but without a filter, more often is bound to be good. al zim
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Phil Planck
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Re: Revisiting the Oil Filter

#2 Post by Phil Planck »

And that's assuming all of the oil went thru the filter each time, but I would think some of it may hardly ever go through the filter.
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Wes Bender
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Re: Revisiting the Oil Filter

#3 Post by Wes Bender »

Phil is correct. To determine how much oil is being actually being filtered would require knowing the flow rate through the filter (and associated orifices) and the flow rate through the bearings, and then comparing the two. Somewhere I've read that only 7% was being filtered at any given time.
Some days it's just not worth chewing through the restraints.....

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Ron LaDow
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Re: Revisiting the Oil Filter

#4 Post by Ron LaDow »

Wes Bender wrote:Phil is correct. To determine how much oil is being actually being filtered would require knowing the flow rate through the filter (and associated orifices) and the flow rate through the bearings, and then comparing the two. Somewhere I've read that only 7% was being filtered at any given time.
Wes, that was the actual result of some testing I did at The Stable back when the Pre Mat Full Flow was in development.
We rigged a 'total loss' lube system, fed from one of those 5-gal fuel jugs (oil in this case), and exhausted the sump into a graduated container and did the same with the outlet from the stock filter. Yes, ~93% of the oil gets 'filtered' by your bearings, 7% through the by-pass filter.
It was published in the Registry at the time (12 years ago?), but I didn't save the 'draft'.
Ron LaDow
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Steve Proctor
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Re: Revisiting the Oil Filter

#5 Post by Steve Proctor »

A logical extension of this discussion would be the question of a revised oil change interval for engines with full-flow oil filters. We know that with the VW beetle with no oil filter at all had a 3000 mile interval. The 356 as well, specifies 3000 miles with its primitive oil filtering system. In 2018, with more modern high zinc oils and a full-flow filter, it makes sense that a 3000 mile oil change is a waste of time and resources. How far, though?
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Dave Wildrick
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Re: Revisiting the Oil Filter

#6 Post by Dave Wildrick »

Steve Proctor wrote:A logical extension of this discussion would be the question of a revised oil change interval for engines with full-flow oil filters. We know that with the VW beetle with no oil filter at all had a 3000 mile interval. The 356 as well, specifies 3000 miles with its primitive oil filtering system. In 2018, with more modern high zinc oils and a full-flow filter, it makes sense that a 3000 mile oil change is a waste of time and resources. How far, though?
For 8 years now, since I rebuilt the motor on my 65C coupe in early 2010 and added Ron's full-flow filter, I've been doing oil changes at 6,000 miles and I have put over 30,000 miles on it before the car got water in the motor and trans from Hurricane Harvey (August 2017) necessitating P/C replacement from rust on rings; heads, etc. were in good shape though.
For 3/4 of that time I used Brad-Penn 20w50 part-synthetic racing oil and for the last fourth, I used Mobil 1 10w40 high-mileage oil (Zn, 900; P, 800; slightly below ideal levels, but so what). No ill effects from 6,000 mile interval oil changes.
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Thomas Frisardi
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Re: Revisiting the Oil Filter

#7 Post by Thomas Frisardi »

Full flow filters were available. Why didn't Porsche use one?

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Ron LaDow
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Re: Revisiting the Oil Filter

#8 Post by Ron LaDow »

Thomas Frisardi wrote:Full flow filters were available. Why didn't Porsche use one?
Probably by the time they were considered part of a modern engine, the factory was working on the 911, and who wanted to waste development money on a car which was going to be discontinued.
BTW, I don't get enough miles on it, so it gets changed about once a year.
Ron LaDow
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Curt Dansby
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Re: Revisiting the Oil Filter

#9 Post by Curt Dansby »

There was a pretty good Registry article on filtration probably 4-5 years ago and I was going to ask the author if I could do a part 2 but you all know how it goes. I have been in the filtration industry for 25 years now and a main focus has been oil filtration and oil and water separation. Ron and me had some back and forth when he was doing the heavy lifting on those calculations and while I have no doubt about the results anything(7%) is better than nothing. Without going into minute detail, a deficit with the factory set up is that the makeup of the filter itself has not changed with technology and is unlikely due to consumption demands relative to modern filters.

The problems are twofold with the canister filter inserts, the media and how it is treated before pleating. The now middle range spin on filters for our modern cars are made of microfiberglass or some hybird( the still high end- Bosch, Mobil 1, etc- are all microfiberglass which is what you want) The inserts are still pleated paper which in and of itself is not bad( it is just much less efficient on three fronts to the MFG) Pleated filter paper, depending on how it is treated is subject to swelling from exposure to gross water(oil that does not reach extended high temps to vaporize moisture from combustion- due to short drives to the beer store). This permanent swelling means the filter goes into bypass meaning your 7% becomes 0%. Now I have no idea how much resin is in the paper Wix/Mahle(now one and the same) or Knecht are using but I would suggest that the production rate is very low relative to the high end filters they are producing and they are likely using the same paper they are using for the $1.99 Fram spin-ons you find at Wal-Mart. I have been the production area at Wix more than once so this hypothesis is more than just conjecture. For you guys with the full flows, stick with Ron's favorite the Fram HP-1(not to be confused with the aforementioned Wal-mart version) My recollection is that Ron did some investigation into can thickness and the HP-1 holds up best to the cold start oil pressures our oil pumps can achieve(this is what I use). If you have pulled all that "needless" heater rod stuff from your car you can probably get away with the Bosch or the Mobil One, but if you want the "best" look for microfiberglass - not microfiberglass/synthetic construction.

To the folks with the factory filter systems I would recommend filter changes based on driving habits rather than miles. Obviously 6K is time to change the oil and filter, but if you just go to cars and coffee 4 miles from the house and do not get out on the road very often you should consider changing the filter on some frequency without changing the oil. To simplify what I inferred above: a inexpensive pleated paper filter can become "clogged" due to swelling from moisture when it has not yet intercepted a single dirt particle.

Maybe Gordon will let me do a serial Pres letter on oil filtration and I can have a respite from coming up with new ideas, but I doubt it. I really should go back and try to compliment the article I mentioned- maybe after the ECH.

"motor oil is motor oil, just keep the engine clean" - Sturgill Simpson
KTF
Curt

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Curt Dansby
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Re: Revisiting the Oil Filter

#10 Post by Curt Dansby »

I forgot to say:
Dave- great to see you in the forum. I thought about you often after Mark gave me the lowdown post the storm.
I hope everything is dry and mold free.
C

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Neil M. Fennessey
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Re: Revisiting the Oil Filter

#11 Post by Neil M. Fennessey »

"Ron and me had some back and forth when he was doing the heavy lifting on those calculations and while I have no doubt about the results anything(7%) is better than nothing."

Curt,

Ron did not do any heavy math lifting; he devised and ran the experiment.

My original calcs are in this PDF. I suspect they helped sell many PreMat Oil filter systems.

Thanks Ron, for my PreMat life-time 50% off discount! 8)
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Oil Filter Flow Calcs for Ron LaDow III 8-21-04.pdf
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Curt Dansby
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Re: Revisiting the Oil Filter

#12 Post by Curt Dansby »

Hi Neil
I stand corrected and my communications with Ron at the time were likely only peripheral in nature.

Curt

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Dave Wildrick
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Re: Revisiting the Oil Filter

#13 Post by Dave Wildrick »

Curt Dansby wrote:I forgot to say:
Dave- great to see you in the forum. I thought about you often after Mark gave me the lowdown post the storm.
I hope everything is dry and mold free.
C
Thanks Curt!
My 64C coupe has been at Al Zim's since before the flood, and Bill Hamilton (Martindale, TX) got the wet 65C coupe back in shape (now at Roger Flink's place--as my garage is full of household items salvaged from the flood).
No mold remains, and I should be moving back into my restored house in less than a month.
Dave Wildrick
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Ron LaDow
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Re: Revisiting the Oil Filter

#14 Post by Ron LaDow »

Neil M. Fennessey wrote: Ron did not do any heavy math lifting; he devised and ran the experiment.
My original calcs are in this PDF. [...])
Correct, and Neil was credited in the article. That math is beyond my pay-grade.
Ron LaDow
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