Did a 500 mile oil change on my Mazda reman and found that the dealership had used an S1 oil filter. Wouldn't have cared at 20k+ miles, but this was the crucial first 500 miles on a rebuilt engine. How concerned should I be?

 

You shouldn't be concerned at all it doesn't matter.

 

I hope you're right but I find it hard to imagine the filters are interchangeable. The S1 filter fits a ton of cars, so obviously Mazda isn't shy about using it where it'll work -- yet they still specced something different for the S2. Doesn't that imply the difference is important?

 

Fodi, how many miles were on your original engine when it needed to be replaced?

 

About 74.5k.

 

The S2's increase in oil pressure is not enough to activate the pressure relief valve in the S1 filter, unless the filter is very dirty. You are fine.

 

Well pro engine builders have been setting up high pressure with thick oil and standard filters like since forever, but the S2 typically runs even higher than those under WOT at high rpm. Over 150 psig is pretty standard on the S2 while 120 psig or so is where most modified S1 race engines run, but they also usually run looser bearing tolerances which tends to bleed off some pressure as compared to them not being looser. When it comes to dp though it’s not just restriction, but also flow. I haven’t ever seen any actual flow data to differentiate the two engines in that regard.

 

OP as most have said you are fine, only issue may arise "if" after long term use and really dirty oil and S1 Oil Filter past it's life/use-by, then yes it would go into oil by-pass and no longer filter oil, that is the reason why there is a by-pass so any engine is not starved of oil in the event the Oil Filter is extremely old, extra long use/mileage and does not filter/allow oil return (blocked).

As S2 owners know the by-pass rating is about twice that of OEM S1 Oil Filter.
Plus the S2 filter is larger/longer (OEM), next time just install the correct one.

S2 Oil Filter By Pass rating is 20.3—26.1 PSI
S1 Oil Filter By Pass rating is 11.4—17.1 PSI

Mazda GENUINE S2 Oil Filter is Part Number N3R1-14-302

As said before it is owners who rarely change engine Oil and or Filter who should be concerned, regular oil and filter change drivers does not really matter.

As I have said before Mazda Japan had this oil filter specifically sourced from Tokyo Roki as it is not used on any other Mazda engine before S2 and still is not.
Where as the S1 OEM Oil Filter dates back from 1986 to 2012 in Mazda 121, then 323,626,E1600,E1800,E2200 vans, Mazda 2,3, Miata, RX-7, T2000,T2500,T4100 trucks.
And is used on most older Mazda before then, like R100,RX-2,3,4,5. Capella 1600, 121L, 929, 808,1300,1600 323, B1600,B2200.

 

Great. Thanks, everyone!

The difference in bypass valve did seem important with all the junk a rebuilt engine might be chucking out in its first miles. But as long as there's no reason to suspect the bypass valve was open a lot, I guess I'll sleep easy. I've been following RacingBeat's break-in instructions, so no more than 4k RPM and no WOT. Thinking about it now, that might have kept oil pressures below the S1 max anyway...

Thanks again, guys. Appreciate the explanations.

 

The S2's increased oil pressure has very little to do with the bypass valve in the filter.

The oil pressure increase in the S2 engines relates to the pressure of the entire flow path. The bypass valve in the filter only matters with respect to the pressure drop across the filter itself.

That's all the bypass valve is for: if the pressure drop across the filter is greater than the pressure to open the valve, then the valve opens to relieve some of the pressure and keep an adequate supply of oil flowing.

Just because the entire system pressure has increase doesn't mean that the pressure drop across a specific part of that system has changed.

Another thing to keep in mind: most of these valves are just metal springs. They are analog rather than binary. So, if the pressure drop across the filter was just high enough to open the valve, it will still pass most of the oil through the filter media. The pressure drop across the filter would have to be significantly higher than the bypass valve pressure to have a dangerous amount of oil go unfiltered.

 

As I understand, pressure drop is proportional to flow rate. So for a given filter medium and state of blockage, the higher the flow rate, the higher the pressure drop.

If the S2's oil pressures are so much higher, I'd imagine its flow rates through the filter are higher as well. That'd mean the exact same filter would produce a greater pressure drop in an S2 than it would in an S1, hence the higher bypass valve rating for the S2.

Someone correct me if I'm wrong.


Great point.

 

Omg..

 

You may or may not be wrong.

Pressure is proportional to flow rate when all other things are equal.
All other things are not equal.

Regardless, if your filter isn't heinously clogged up (it probably isn't) and you've been maxing it out at 4k RPMs, I don't see how you'd have achieved pressure drops across the filter great enough to matter.

 

I think this is some kind of surreal contest, in which they try to out-overthink each other. I don't know for sure, but I'm getting popcorn and a beer!

 

You mean we're not supposed to continue down the rabbit hole long after the practical concerns have been settled?

I thought this was the Internet!

 

IamFodi is a willing participant. This is a victimless crime.

Let me have my fun, damn you!