Filtration improvements with increased mileage?

[digitalSniperX1]

I change my oil every 3k miles. I do that for many reasons but suffice it to say i get about 5 of 7 quarts out with each change, so it's effectively every 4200 miles.

I do not however change the filter with each change. I've been using the Amsoil filters (EaO?) and as the filter accumulates miles, the filtration seems to improve. I don't know about filtering efficiency of course but the oil seems to stay cleaner during the OCI. In fact it's still somewhat clear after the pro-rated 4200 mile change. I intend run these filters for 3 OCI's.

Anyone else notice increased filtration as a filter ages?

 

[mechtech2]

I have heard the theory, and it is possible. But if the filtration gets better, the flow would have to be reduced somewhat.

 

[Malo83]

Never understood this, why would you run clean oil thru a dirty filter??? and then thru 3 OCI's. I do 3K OCI's also but I change my filters out.

 

[Gary Allan]

Well, you wouldn't buy an expensive filter for 3k OCI's ..and while you can do it, there's little sense in using a cheap filter for 10k+ OCI's when you can get your money's worth out of a finer filter.

Let's put it this way. If you changed out your oil @ 1500 miles, would you still change the filter?

I've run an EaO for 3 x 5k + 3k.

 

[digitalSniperX1]

Exactly. Plus larger environmental concerns are with the filter.

No reason to throw away a 13 dollar filter each oil change. These Amsoil filters are top notch.

 

[digitalSniperX1]

I would think so also. I'm not really concerned about that. It's more that I'm impressed with the oil's condition after changing it out.

In my case here also, the filter is pretty tiny. I seriously doubt it would hold 8 oz.

 

[06VtecV6]

Originally Posted By: digitalSniperX1



Anyone else notice increased filtration as a filter ages?




I know it definitely applies to engine air filters but there is a point where the law of diminishing returns makes it bad and better to replace it. Does an engine oil filter work the same?

 

[XCELERATIONRULES]

It doesn't make sense to me to run dirty oil through a new filter,or running new oil through a used filter.
Both contaminate each other.
If I was walking through the auto parts store and had $12 in my pocket,and could choose either an oil filter or a dino oil change,I would chose the dino oil.

 

[digitalSniperX1]

I do not think the filter is "bad" after 3k miles. I believe Amsoil says these filters are good to 15k miles. I plan to use them 9k miles.

The RX-8 has 2 oil coolers and they hold the 2 quarts of oil hard to get at. It's far more difficult and time consuming to get all the oil out of them rather than decrease the OCI.

The reason for the short OCI is that rotary engines run very rich and are known to dilute oil with gasoline. After 3k miles, the oil isn't so contaminated with solids as to require changing. The filter is/was doing its job. And it continues to do so after 3k miles, in fact, it appears to filter better. I was wondering if anyone else had similar experience.

 

[Gary Allan]

Filter do improve as they age. It's pretty hard, imo, to saturate a filter to the point of having a static PSID that would cause perpetual bypass activity. As it ages, the PSID will tend to be more effected by viscosity ..just as it would in higher terminal flow ratings when new. For example, most filters have manufacturer spec's that rate it for PSID at a given flow rate for a given visc. Now it's sensible to figure that if you block half of the filter, you'll have a higher PSID, but that doesn't mean that THAT figure is anywhere near breaching the bypass limit ..nor that it amounts to any significant PSID after warm up. It does throw a "reactive" component into the total scheme, but it can be, imho, be ignored by most.

As far as contamination from residuals?? Not even a blip on my radar

 

[digitalSniperX1]

I'd like to see composite plots of filtering efficiency as a function of miles driven and pressure differential. I believe they'd say exactly what you have stated here.

The plots I've seen for new filters being functions of the variables you've stated above show very low pressure drops across the filter media for the viscosities used in the measurement. Of course these were new filters.

I don't know how bypass valves work but I assume they are activated on pressure differentials.

In my particular case, there is apparently no bypass activity going on as the filter is by visual inspection continuing to do its job and doing it well.

While it may be overkill, I won't be using any other filter in this vehicle or any other vehicle I own.

And finally, my decision to not change the filter has little to do with 15 dollars and far more to do with just avoiding wasteful practices combined with the fact I've found no one close by willing to take used filters.