Oil viscosity questions pertaining to oil filters

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MrRPM

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Are oil filters built to use oil viscosity their original application calls for? As in my jeep calls for a PH16(fram)/14670(purolator) sized filter. my jeep also calls for a 30wt oil, does this mean the ph16/14670 sized filters are made to use 30wt oil? does viscosity affect oil filters at all? What if I am now running an oversized filter spec'ed for a different vehicle? are the bypass valves still set for the same pressure? even if the vehicle applications call for a different weight oil?

not that its possible but, what if you ran a filter commonly used for 0w-20 oil and some how used it on an application that called for 15w-40 oil. will the bypass valve open up immediately expecting thin 20wt oil? or is this not how it works at all? or does this mean we should be using filters close to the viscosity their original application calls for? what if someone with a vehicle that requires a 20wt puts in a 50wt oil, is their filter bypass going to open up more frequently then it should because of the excessive visocity?

I guess I can't find a clear answer googling it so I'm asking here
 
Originally Posted By: aquariuscsm
My car for example,lists 10W30-20W50,but only one filter is spec'd for it.


and so does using 20w-50 cause the bypass to be open more often then using 10w-30? thus filtering less oil?
 
Last edited:
Originally Posted By: MrRPM
Originally Posted By: aquariuscsm
My car for example,lists 10W30-20W50,but only one filter is spec'd for it.


and so does using 20w-50 cause the bypass to be open more often then using 10w-30? thus filtering less oil?


Could happen ... mostly at cold temps when the oil if much more viscous. The oil viscosity plays a large part in how much delta-P is seen across the media which causes the bypass valve to open if the delta-P exceeds the bypass setting.
 
Originally Posted By: MrRPM
Originally Posted By: aquariuscsm
My car for example,lists 10W30-20W50,but only one filter is spec'd for it.


and so does using 20w-50 cause the bypass to be open more often then using 10w-30? thus filtering less oil?



Man I have no idea.
 
The original ENGINE build chooses a filter based on the expected oil flow needs and expected operating temperature, and the intended oil viscosity. The filter isn't customized to the viscosity at all, the same filter may show up on a different engine with wildly different flow and viscosity needs.
 
I'm testing this right now in my F150 with a DP gauge setup and the only time the filter comes close to bypass is when the oil is cold and thick. I'm working now with an oil that is thicker than spec'ed (10W30 when spec is 5W20). I am driving sedately but when I don't I'm right in the area where the fiter will go into bypass.

440 has it right. It's about the bypass setting of the oil filter...whatever that is.

Thicker oil will cause generally cause the bypass to open sooner and vice versa. The designers want the filter to bypass as little as possible, so the filter will be spec'ed/chosen with that in mind. BUT if you took an engine that was spec'ed for 0W20 and put 15W40 in it, you would see more bypass events in normal operation than with the 0W20. If you did the reverse, the opposite would be true.
 
So then, different filters have different bypass settings and manufactures choose what filter they want to use based on engine oil pressures, flow rates, and oil viscosity.

Anyway to tell each filter's bypass setting?

kind of makes using an oversized filter a risk hoping it uses the same bypass setting as the OEM size
 
Originally Posted By: MrRPM
So then, different filters have different bypass settings and manufactures choose what filter they want to use based on engine oil pressures, flow rates, and oil viscosity.

Anyway to tell each filter's bypass setting?

kind of makes using an oversized filter a risk hoping it uses the same bypass setting as the OEM size


I think part of the bypass setting equation is based on the media being used (ie, flow restriction factor), and the area of the media. Both of those factors play a big part in what the delta-P across the media is vs. oil viscosity & flow rate parameters. Another factor is how much delta-P can the media take before it tears/fails.

If the media can flow better then the bypass setting doesn't have to be as high. And if the media can take more stress from the delta-P, then the bypass valve can be set higher.
 
Originally Posted By: ZeeOSix
If the media can flow better then the bypass setting doesn't have to be as high. And if the media can take more stress from the delta-P, then the bypass valve can be set higher.



The OEM oil filter on my 2013 Subaru Outback 6-cylinder has a bypass rating in the 23 to 25 range. Does Subaru need such a high bypass setting because "the media can take more stress from the delta-P"?
 
Originally Posted By: 147_Grain
Originally Posted By: ZeeOSix
If the media can flow better then the bypass setting doesn't have to be as high. And if the media can take more stress from the delta-P, then the bypass valve can be set higher.


The OEM oil filter on my 2013 Subaru Outback 6-cylinder has a bypass rating in the 23 to 25 range. Does Subaru need such a high bypass setting because "the media can take more stress from the delta-P"?


There have been many threads about why Subaru might need a higher bypass valve setting. Main theory is because they have pretty high volume oil pumps. If the filter goes in to bypass at 23~25 PSI, then obviously the filter designer has made it so the media can take that delta-P.

As said earlier, the bypass setting has a lot to do with the filter's design too, like the media flow resistance and media total area, which defines the overall flow resistance. That's why different filter brands for the same vehicle may show different bypass setting values.

Look at this thread, and see that the PureOne tested only has ~5 PSID at 12 GPM of hot oil flow (viscosity of 10W-30 @ 200 deg F). I think the Subaru oil pumps put out around that amount of flow rate, so if that's the case the filters that have a 23~25 PSI bypass setting must need it because they are somewhat more restrictive to flow, and/or the designers want a safe margin for media loading and cold start-up to prevent bypass events as much as possible.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2088643&page=1
 
I don't have an answer to the original question. However, I have noted that at least some filter companies state in their warranties that the coverage only applies if the OEM recommended viscosity is used.
 
Originally Posted By: Garak
I don't have an answer to the original question. However, I have noted that at least some filter companies state in their warranties that the coverage only applies if the OEM recommended viscosity is used.


Thing is, most owner's manuals or service manuals will show a range of acceptable oil viscosity. The filter designer must take that in to account also ... meaning they should assume the thickest specified oil by the vehicle manufacturer could be used by the owner.
 
What happened to the days you just buy the spec'd filter for the engine it fits, install it, and go on your way?
21.gif


J/K! I'm curious as to the OP Q? also.
thumbsup2.gif
 
True, ZeeOSix. I suspect they're not worried so much about the guy running 5w-30 in a 5w-20 application. They're likely worried about the guy running straight 50 in the winter and in questionable mechanical condition to start (i.e. pre-existing conditions).
wink.gif
 
Here's my take. It all depends on the pressure differential of the filter. Some have low numbers some have high.

I would think a thick oil and a 8 lb bypass is going to bypass quite a bit when cold

On Hyundias they use one spin on filter for most of their engines. It has a 20 lb bypass. This filter is used on all kinds of engines and on my particular one they recommend anything from 5w20 to 10w40. On my car when I start it when cold the oil pressure at idle will go to 75 lbs.

Another thing is some Motorcraft filters which have the bypass at the top of the filter. That way all the [censored] that has settled will not be flushed into the oil galleys when the car is first started.
 
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