Ok, I vaguely remember someone saying to use the factory oil filter only. Something about an oil bypass or something? The reason i ask is, about the same time I started having problems with my car I also changed my oil filter without much thought, just looked up a replacement filter and bought it. Now, would this change in the filter show on my oil pressure gauge also? My gauge used to show a steady 80psi even after it was warmed up at idle, but now it goes down to about 65-70 after it warms up. Could the change in filters do this? thanks for any replys.

 

[QUOTE] I vaguely remember someone saying to use the factory oil filter only. Something about an oil bypass or something?

I think the bypass valve opens when the filter is dirty and clogged.. the bypass valve opens up to maintain oil pressure, and the oil "bypasses" the filtering part of the filter.. it shouldn't affect oil pressure during normal operation.

[QUOTE] The reason I ask is, about the same time I started having problems with my car I also changed my oil filter without much thought, just looked up a replacement filter and bought it. Now, would this change in the filter show on my oil pressure gauge also? My gauge used to show a steady 80psi even after it was warmed up at idle, but now it goes down to about 65-70 after it warms up. Could the change in filters do this?

Your oil pressure reads very high at idle, and apparently always has?.. it could be a variation in the sending unit (so the signal would read consistently high). But still.. that reading is WAY high for IDLE pressure.

The change from 80 to 65-70 could be due to the filter's specs.. what brand are you using? I use Mazda or Pennzoil filters, and have never had a variation in my readings.. they seem equivalent in that respect.

 

Ok, to bring this into perspective, this is the reading that my aftermarket oil pressure gauge tells me. The stock gauge fluctuates so its' not very accurate. I believe it's a cheap purolator, but i just purchased a case of oil to do an oil change but have not gotten a filter yet. One other thing, I noticed when i park in reverse next to a fence, there is black marks on the wood like oil or soot or something. It looks to be oil, but my engine doesn't smoke at all or anything. carbon deposits from the exhuast maybe? Oh and before i forget, yes before the filter change that was the reading.

 

I think you should only use the Mazda thermostat because of the bypass valve. Oil filter shouldn't matter.

 

ever notice how small the mazda oil filter is?? I use pure-one oil filter...about 5 bucks...suppose to be a good one. I don't think oil filters effect the oil pressure gauge....these gauges are not that accurate anyway...and..wow..I thought I had a high pressure reading!! mine reads 70 at 60 MPH...idle is 30-40...I have a gsl-se...cjf

 

You havent seen the new Mazda filters, I had my oil changed the other day at the dealer.. Yeah Yeah Yeah I know, but it was only $15, and I made sure they didnt use that bulk oil **** they have... The new Mazda filter is like 1 inch maybe 2 taller now

 

Those reading sound exactly like my 88 vert and my 85 Cosmo POS

 

The valve in the OEM filter is called an anti-drain back valve. It keeps the oil from draining out when the engine's off so you get quicker oil pressure on start-up. It has nothing to with oil pressure once the engine's running.

 

Rev, plenty of aftermarket filters have the anti drainback valve. I just got thru studying this subject and after many hours of reading and picking peoples brains I bought a purolator L20073. Its for an Rx-4 and is taller than the standard rx7 filter, more filter area, less oil pressure drop across the filter. I will install it next oil change. Heres one of the articles I used for my research.
http://www.scuderiaciriani.com/rx7/oil_filter_study/

 

i do LOTS of rx oil changes... thats my job and I ALWAYS put on a mazda filter... on a bonger i dont give a rats ***.

 

So then is my pressure bad? i can give the throttle a blip at idle and it instantly jumps to 80 psi.

Oh yeah, this is at about 1100 rpms at idle.

 

The Mazda oil filter is small but well constructed and packed with filter paper element. It does have an internal bypass valve that opens at 14 psi when cold and at high RPM may allow dirt to pass through. Let your car warm up well before gunning it and you're fine.