Subaru oil filter on a Honda?

[Blagoje]

Do any Honda dealers leave the filter on when they change the oil? “Your car is ready sir, next time we will change the filter?” I don’t have any data as I never went to one. I have a suspicion they change every time. Some makes don’t say use filter twice in the manual, some do. For one thing they would have to have some kind of record from the last oil change to know if the filter was on it’s first use. I don’t think they will spend the time in that research.

This may not have as much to do with whether or not any Honda dealer or anyone else uses a filter for two consecutive oil change intervals but rather that Honda, as in Honda corporate, finds this to be permissible as a SOP. I stated what I stated in relation to this specific concept because we're trying to get to the bottom of why the Honda bypass spec may be so much lower as compared to Subaru.

Here is a scenario: Is an oil filter more or less likely to experience bypass events in the event that it becomes more saturated with debris? If the answer is more likely then over the course of an extended usage interval in order to maintain an uninterrupted oil flow a manufacturer might consider setting the bypass spec lower to accommodate that variable. @ZeeOSix am I making any sense?

 

[TC]

Going back to the basics, did we ever get:

-The Subaru filter part number?
-The year/model/engine of the Honda?

 

[Fair enough]

This may not have as much to do with whether or not any Honda dealer or anyone else uses a filter for two consecutive oil change intervals but rather that Honda, as in Honda corporate, finds this to be permissible as a SOP. I stated what I stated in relation to this specific concept because we're trying to get to the bottom of why the Honda bypass spec may be so much lower as compared to Subaru.

Here is a scenario: Is an oil filter more or less likely to experience bypass events in the event that it becomes more saturated with debris? If the answer is more likely then over the course of an extended usage interval in order to maintain an uninterrupted oil flow a manufacturer might consider setting the bypass spec lower to accommodate that variable. @ZeeOSix am I making any sense?

I was diverting a bit. I understand the mission. Don’t know if it is ever going to be possible to know what the companies reasons are. They must match the media, bypass spring, oil pump, and oil viscosity as they feel best for all uses the product is sold for. As far as microscope pictures show most oe and the Subaru Roki media in particular look quite porous. Different engineers in the companies may favor one factor over another and the bypass spring setting. Maybe they were arguing about it in the same company who knows.

 

[ZeeOSix]

An additional thought I had was that the Honda OEM oil filter is made to use on two consecutive OCIs and this is coming from Honda directly. The Honda recommended OCI is not to exceed 10,000 miles, so they allow for the OEM oil filter to be used for up to 20,000 miles which would suggest that it may become saturated and bypass events are more likely to occur. To accommodate for that likelihood they have set the bypass valve to a lower setting.

Typically a filter designed for a long use like the possible 20K miles in the Honda case, the filter would be designed to handle the anticipated loading over that use period, and the bypass valve would be set higher than not to ensure less bypass events. More media area helps to achieve higher holding capacity, and less efficient filters seem to have more holding capacity because they are constantly shedding debris down stream and it takes more captured debris to get the dP across the filter to the point of defined max holding capacity.

I'm not sure what the Honda filter bypass setting is, and if it differs depending on where the filter is made. Bypass valve settings are somewhat dependent on the filter itself depending on its flow vs dP curve, and of course for the anticipated max engine flow and loading factor over the recommended OCI. A bypass valve setting can be measured pretty easily with a force scale and some measurements and a calculation.

 

[ZeeOSix]

The pumps do wear and increase internal leakage over time, and with more pressure, there would be more internal leakage, but that is more of a low viscosity oil at high temperatures, problem I guess?

Yes, oil pumps can wear some if the engine is highly neglected from oil changes. A badly worn pump would show lower than normal oil pressure at idle and low RPM. If it's still healthy enough to hit pressure relief at some RPM, even if worn and has more pump slip, then the pump slip doesn't matter at that RPM and above. New PD pumps in engines typically have around 15% pump slip, and since oil pumps are over-sized to obtain a good flow at idle, they will go into relief at a pretty low RPM, and at that point the pump slip doesn't matter anymore. And they are over-sized to provide plenty of oil flow at idle even with the normal pump slip. The filter bypass valve has no bearing on how the PD oil pump performs.

On a cold start probably even a quite worn oil pump doesn't have much blow-by, and even less with higher viscosity oil, but don't thinner oils get to the top end of the engine faster than higher viscosity oil on cold starts? That might be more to do with smaller oil passages not flowing nearly as well as the larger ones at very high oil viscosity?

Cold starts need to use the correct "W" grade to ensure adequate cold start lubrication in terms of getting oil to the force fed components, as well as lubrication supplied by "splash". Tight passages that are force fed are still getting plenty of oil, it will just cause the oil pump to operate at higher pressure, that's why oil pressure is always higher at the same RPM when the oil is thicker. That's the whole reason that positive displacement oil pumps are used on engines - to ensure adequate oil flow and lubrication at all operating temperatures.

With older tractors I find you get more hydraulic pressure in the rams with higher rpms, when you are trying to lift something a bit too heavy like popping out a stump, but that might just the blow off valve opening progressively and allowing higher pressures with higher flow?

Hydraulic systems like that are fed pressure by a PD pump also, so higher RPM is going to produce more hydraulic pressure up to the point where the system controls the pressure to a maximum so it doesn't blow something up in the system. Same with the pressure relief valve on an oil pump on an engine.

 

[Fair enough]

Maybe Honda tests their engines for all this debris load and they found the oe oil filter can go two times. Not other filters, just theirs. Subaru engineering found they need higher bypass. I don’t know how anyone can find out why they do what they do by thinking about it. it’s made up of individual engineers in a company, maybe one is overbearing and gets their ideas adopted over everyone else. It doesn’t seem very important in these times.

 

[ZeeOSix]

This may not have as much to do with whether or not any Honda dealer or anyone else uses a filter for two consecutive oil change intervals but rather that Honda, as in Honda corporate, finds this to be permissible as a SOP. I stated what I stated in relation to this specific concept because we're trying to get to the bottom of why the Honda bypass spec may be so much lower as compared to Subaru.

One thing about Subarus is that some of them have an insanely high flow oil pump. That will have a bearing on the filter's bypass setting. Also, we don't really know what the OEM Subaru filter's dP vs flow performance curve looks like. If it has relatively high dP vs flow the the bypass valve will be set higher too. If a filter bypass valve is set pretty high, then the filter designer better know what impact what would be on the oil pump output reduction (by putting the pump farther into relief) if the filter bypass valve got to that level of dP. That's one thing I'd be concerned about if the bypass valve was set really high, but there are lots of filters with 23+ PSI bypass valves, so the oiling systems on those engines must not care too much about that high setting. In the case of the Subaru, it's pump output is so high that if the filter was at 23+ PSI of dP then the pump output is still more than adequate flow to oiling system.

Here is a scenario: Is an oil filter more or less likely to experience bypass events in the event that it becomes more saturated with debris? If the answer is more likely then over the course of an extended usage interval in order to maintain an uninterrupted oil flow a manufacturer might consider setting the bypass spec lower to accommodate that variable. @ZeeOSix am I making any sense?

Yes, as the filter loads up with debris the dP vs flow goes up. How fast the dP increases is dependant on the media design and the total media area. But like I mentioned earlier, if a filter is expected to be ran for a long OCI period the designer should be using more than enough media area to take care of the anticiapated debris loading, and might also bump the bypass valve setting up some to ensure less chance of the filter bypassing too much near the end of the use period. Engines that are well mantained aren't doing to load up a filter very much over a recommeded OCI unless the engine has been neglected or a cleaner or something like Valvoline Restore and Protect is being used in a dirty engine.