Flat cut seal vs P profile seal ... why ?

[geeman789]

Why do many OE filters use a round, or P profile seal ? My Honda and Subaru both use round filter seals, but after market filters are always flat cut, even on premium filters like the Fram Ultra.

Does the P-profile seal just work better ... ? Is it less expensive (seems unlikely ), or easier to remove, or just a better seal ... ?

Thoughts ?

 

[WellOiled]

Flat gaskets are faster, cheaper and easier to make. I do not know about the performance differences.

 

[ZeeOSix]

P-profile (or O-ring type) gaskets are typically designed for when the filter is tightened until the base makes contact with the filter mounting seat - Denso/Toyota filters are that way. Personally I don't like the filter can digging into the filter mount seat so I stopped using them (and for other reasons too).

Filters with flat gaskets don't bottom the filter base onto the mounting seat. There's usually 0.5-1 mm of air gap when the filter is fully tightened.

 

[WellOiled]

Originally Posted by ZeeOSix
P-profile (or O-ring type) gaskets are typically designed for when the filter is tightened until the base makes contact with the filter mounting seat - Denso/Toyota filters are that way. Personally I don't like the filter can digging into the filter mount seat so I stopped using them (and for other reasons too).

Filters with flat gaskets don't bottom the filter base onto the mounting seat. There's usually 0.5-1 mm of air gap when the filter is fully tightened.

I have had filters with flat gaskets bottom out. I bet the gasket was cut too thin. I believe they were Rock Auto close outs.

 

[Yah-Tah-Hey]

The "P" style are an O-ring arrangement with engineered controlled deformation. That is how an O-ring works. I haven't had a problem with Denso oil filters damaging the purchase. Tighten them until they stop and that's it. The O-ring is deformed per spec and seals every time.Did I mention that I like Denso filters?

 

[ZeeOSix]

Originally Posted by Yah-Tah-Hey
Tighten them until they stop and that's it.


That's the part I don't like ... the filter will contact and scar the filter mounting base to some degree. Might be OK if you always use the same exact filter, but maybe not if different filters are used and the gasket location isn't exactly the same between oil filters.