Huh?

I added the CAT filter at 16k miles, and changed the factory fuel filter at 16500.

I changed the CAT again at 27k, and now at 29k (going with the factory 15k interval for factory fuel filter) I saw it open to find it all dirty.

I thought the CAT filter should keep the factory filter perfectly clean, as it is downstream of it..............No?

When I changed out the CAT filter, I sawed it open, and it was a tad dirty, maybe 20%.

This is odd.........

a different color doesn't mean it's dirty.

Any filter passes micron size stuff, if u look at Nick's fuel test after the Cat, u still have stuff getting bye.

So that is the picture...two sides of the OEM with about 13k miles on it? You replaced the CAT at 27k and did it look dirty? At that point your OEM filter might already be as dirty as shown.

The CAT at 29K should look clean since it only had 2k miles on it...right?

Key here is there is no rust at the OEM...and you have been running the bio.

I also note that the color is black on the OEM...even when I ran just B20...I never got the black color again on the OEM or any of my filters...only with D2.

Finally...you can still get stuff through to the OEM based upon what you put in to begin with...filtering is a percentage of what goes in...so if it is dirty enough.....

Maybe the quality of your D2?

Ron, I think you are reading me wrong.....

The truck was stock until 16k. At that point, I added the CAT filter. 500 miles later, I changed the stock filter.

I changed the CAT again at 26k, and now at 29k I changed the factory filter (the one in the pic.)

So the pictured fuel filter sat downstream of the CAT all its life, and still got that dirty. It just seems odd to me......If the CAT filter is 2m and 99% efficiency, it seems like it should have caught everything and left the factory filter perfectly clean. ?

But yes, I was glad to see no rust/other stuff in either filter when I cut them open.......

When in town, I buy the fuel at a real high volume cardlock, but I have made a few trips out of the area where I just fill up wherever I find the cheapest D2.

No filter is truly 100% so what you see is normal. I do believe that the first filter and most frequently serviced filter should be the OEM unit. This will keep the warranty folks happy too.

The 2um 99% efficiency rating is a nominal rating and typically ratings are based on multipass etc...

I'd say that the OEM is the one of the cleanest I've seen if it had 13k on it. You can thank that CAT for that! The discoloration of the OEM is minimal. Very little stain at all. If'n it was me, I'd think you could go 2x the exchange frequency on the OEM and sleep peacefully. Dat CAT is doing its job!

I'd say that the OEM is the one of the cleanest I've seen if it had 13k on it. You can thank that CAT for that! The discoloration of the OEM is minimal. Very little stain at all. If'n it was me, I'd think you could go 2x the exchange frequency on the OEM and sleep peacefully. Dat CAT is doing its job!

:exactly:. Your filter looks about the same as mine did at 10K with the cat prefilter. If you didn't have the cat the OEM filter would look much much worse.

That filter is very clean.

Cut open the paper pleats and take some more pictures. Do the same for the CAT.

CUL
Marco Polo

yes that filter is very clean indeed. i could show you pics of an OEM filter with less miles than that one, which is black as night with a filter can full of rust. if i were you i'd be quite happy! plus you'll save money given the cat filters are cheaper and last longer than your OEM.

and as RonJT said- no rust.. especially running bio.. you're prefilter is surely doing its job!

Oh well in that case........:grd:

I bought the OEM filter at NAPA, and they said the pn had changed, and the filter is different.......Also more expensive........

You got the dual pleated type. More is Better & More expensive!