Anatomy of Oil Filters

At the "Geek-Out" at George Roffe's home on Friday, November 27, 1998 we Cut open five oil filters using a Dremel Tool cut-off wheel. Four of the five are shown directly below. They are: Nissan (early SE-R), Mobil 1, Fram, and Purolator.


Click on each filter for a close-up view

Here are all five with the filters dissected
Click on a filter to see a larger view.
  1. Oil enters the filter through the small holes on the outer edge of the base flange. It then goes through the filter and exits to the engine through the center hole.
  2. All the filters have an anti drain-back valve. It is a rubber membrane which covers the perimeter holes in the base flange and is pushed aside by the oil as the oil enters the filter case. With the engine off, the membrane is covering the holes, and prevents oil from draining back into the engine.
  3. The pressure relief valve causes the oil to bypass the filter element if the filter becomes plugged or the oil is so thick (cold) that there is significant back-pressure from the filter.
  4. The Nissan (early) filter has no pressure relief valve (all the others do). If there is significant back=pressure from the filter, there will be a serious loss of oil flow.
  5. The base gasket on the Mobil 1 filter is similar to the Nissan filters, rounded. The others are flat.
  6. The Mobil 1 filter is smaller than the others, but its filter material is thicker.
  7. The Fram filter has cardboard ends. All the others have metal ends.
  8. The pressure relief valve of the Fram filter is in the hold-down. The hold-down seal is to the cardboard filter top. If it leaks, oil will bypass the filter element.

More Filter Information From the SE-R Mailing List

This information is from the Purolator oil filter cross reference manual at PEP Boys. 

Filter
Model   OD    ID    Lgth.       Model Used On
L10241 2.98 3/4-16  3.42        (???)
L14476 2.56 3/4-16  2.95        ('92 Toyota Paseo)
L14477 2.56 3/4-16  3.54        ('91-94 Sentra SE-R)
L14620 2.56 M20x1.5 3.57        ('94 Mazda 626/929)
L14622 2.56 M20x1.5 2.98        ('95+ 200SX SE-R)
From the info above, you can see that there are two differences between the Classic and 200SX filters, the Inner Diameter, and the length. There is no difference listed in the Classic between low port and high port. The difference in length is to fit into the more cramped area in the 200SX, the Classic had slightly more room to get the filter in (amazing as that sounds for you Classic owners).

The only significant difference appears to be in the threading, the Classic uses 3/4-16 threading, and the 200SX uses a metric threading of M20x1.5. These two threads are NOT identical, but are extremely close. Several folks on this list have used the 200sx filter on their Classics. I don't know of anyone that has tried to use a Classic filter on the 200sx, mainly because of the length difference mentioned above.

In the chart above (ignoring the first entry), there are two short filters, one with metric, the other with standard threading, and two longer filters, again with a choice of threading. To the best of my knowledge, these are interchangeable, though they are NOT a direct cross reference.

The only reason I have for working all of this out was so that I could use the Purolator PureOne (high filtration) filter on my car. They don't make one for the SR20DE motor of any flavor, but they do make them for the other two non-SR20 cars listed in the chart. On my Classic, I'm now using the PL14620 filter, which is just barely longer than the normal Classic filter, but with the 200SX threading. It screwed on just fine.

The first filter listed in the chart was suggested by one of the list members here for his Classic, again because it was available in the PureOne line of filters. The only difference on this one was the outer diameter being slightly larger, this is the diameter of the O-ring, and the only reason I don't recommend this one is because I do not know if this larger ring will seat properly on all cars, I don't know what the tolerances are, and I'd hate for someone to have all their oil leak out because the filter didn't seal properly. !