Hi all,

OK I need to have a few simple questions answered concerning oil filters. An oil filter has a large threaded hole in it's center and 6 or so small holes around the large one. What is the direction of oil flow? I believe it is in the 6 small holes and out the large one. Is this correct?

What started me thinking all this "oil theory" stuff is, today I changed the oil in my 4 vehicles. One of them had not been run in a day or so and when I removed the old filter I was surprised to find the filter empty of oil. This filter sets in a horizontal position and I figured the oil had ran back into the block. Anyway, I was concerned enough to cut the filter open and see just how it is made. The only way I can figure out the oil flows through it is "in" the small holes, thru the filter element, then out the large hole. I base this on there being a one way valve of sorts covering the small holes. There is also another valve at the base of the filter that would allow oil to bypass the filter element all together. I guess that this is needed in case someone never changed their oil and the filter became stopped up.

Now for my last question. Does all of the oil that flows out of the oil pump flow through the filter? Someone was telling me that only a percentage of oil actually goes thru the filter. I thought all oil went through the filter.

Thanks to all,

 

You are basically correct, the oil flows from the outside of the filter media to the inside.

The one-way-valve on the small holes is the "anti-drainback valve". Sounds like your empty filter didn't "anti-drainback" ...

The oil pump has a high-pressure bypass valve that when the oil pressure is high, the pump will actually dump excess oil straight back into the oil pan. That may be what they mean by not all the oil going through the filter.

There is also a high-pressure bypass built into the filter, where if the media gets clogged enough (or your just asking too much of the filter), it will bypass. The basic theory is "dirty oil is better than no oil", which is true, at least most of the time.

 

By the way, I'm sure someone will chime in with "is it a Fram?" ... and yeah, I've heard many a sob-story about Fram filters not doing the "anti-drainback" thing.

I've never had it happen to me, in 20 years of changing oil filters. It HAS happened to others, so hedge your bets.

 

Thanks for the replies,

As a matter of fact yes it was a Fram oil filter. I have seen this drain back thing happen on 2 different occasions and both were Frams.

Is it time to change filter brands? I thought Fram made good filters. I have used them exclusively for 20 years.

What is the most popular brand?

Thanks,

 

Popular brand.............Motocraft FL1A !!

Dont leave home without it.

Larry

 

There are two new versions of the Fram filters, the best being the XG series. I took them apart and they are at least as good as the Motorcraft, but pricey, I think an XG2 (modular 4.6L/5.4l/V10) was $12 last time...

I used the XG2 in my V10 because it called for a silicone anti-drainback valve (FL-820S - notice the S).

 

The 351 Cleveland engine in my 72 Torino always had a cold start rattle using the Fram PH8A. I switched to the Wix 51515 and immediately the rattle vanished on cold starts. I use Wix oil filters exclusively and neither my 72 torino nor my 76 F100 have any rattle on cold starts even after sitting for more than a week at a time.

 

Yep. I switched to Wix and will never look back. FYI, Napa oil filters are Wix, and the "gold" is the equivalant to the 51515.