oil filter drain-back?

it's been ages since i've tried many other brands of filters, but maybe
y'all can let me know...

has anyone here done an oil filter drain-back test on their honda?
basically, when changing oil, rather than bring the motor up to temp,
then drain immediately, bring it up to temp, then drain after 30-60
minutes while still warm, but having left time for everything to run
back to the oil pan.

i find that invariably, honda branded filters are empty after this time.
i would expect them to still be full of oil if the one-way valve were
working properly. similarly, i've tried this with denso, and they empty
out too. cheapo woolmort supertech filters otoh retain oil perfectly.

i used to do this "test" unintentionally with honda filters, more
because i wanted to minimize spillage than anything else. but since
messing about with the supertechs, not a single one has drained.

what do others find with different brands?

[i was using the supertechs as an experiment - i read that the filter
media was very high quality. they do seem to keep oil looking clearer
longer, but that's not scientifically assessed, just eyeballed.]

 

That's odd, because I find Honda filters retain oil very well, remaining
full long past shutdown.

Your primary source of drainback is NOT the anti-drainback flap, but the
filter medium itself. The Honda medium is dense enough that oil has
trouble flowing through it except under pressure, so once the center
pipe drains, in does not refill with oil from the dirty side.

Too many aftermarket filters have looser media that allow oil to flow
while not under pressure. These will drain the dirty side to half
capacity (or less) after shutdown.

A quick test for next time you do oil changes:
Remove the filter, dump any remaining oil out of the center pipe, then
place the filter on the ground, open end up. You should find aftermarket
filters will gradually refill the center pipe after sitting for a time,
while Honda-branded ones won't.

 

Also, perhaps weigh a new one and see what it weighs after you
change it out. There will be some increment from the crud and
the wetted surfaces, of course.

 

doesn't compute. only if the media is utterly clogged could that
happen. and a filter that only flows under pressure is a scary thing.

if removed shortly after shutdown, honda filters do indeed continue to
equalize levels, but as i stated earlier, i've found that honda filters
always drain when left on the block for 30-60 minutes. that could
/only/ be something to do with the drain-back valve. this is something
i've found to be consistent over years and different honda filter batches.

 

have to compare wetted new and wetted old for that. but i doubt that
all the contaminants from 10k miles add up to more than a couple of grams.

 

Try it before you deny it. This phenomenon has manifested itelf before my
eyes repeatedly over the course of 16 years.

 

but i have!

you're describing a filter with a functioning anti-drainback valve.
only a clogged filter can prevent "refill", or what i'm describing, an
empty filter because the valve is malfunctioning.

 

So do I, I only included it for completeness. But it may be an interesting
exercise. I thought that the anti-drainback device was to protect the
motor during start-up, so have filters got a lot smaller over the years?
Or have the pumps got a higher flow rate?

 

filters have gotten smaller, but that's nothing to do with drainback.
the valve is supposed to be to stop crud draining back into the oil pan
once it's in the filter,

nope. not necessary either.

 

Understood. Thanks Jim.

 

Filters I've used over the course of many years that do NOT allow
refilling of the center pipe after initial drain:
- OEM Honda (made in Canada by FRAM)
- OEM Toyota (made in USA by somebody else [Filtech?]).

Filters that will repeatedly refill the center pipe after initial drain:
- Most aftermarket, including FRAM filters that use the /exact/ same
anti-drainback flap as OEM Honda.

------------

A filter medium will allow fluid flow in BOTH directions. It is critical
to realize that.

Consider this, therefore: When you place a full filter open end up,
there is an empty center pipe. The natural tendency for the oil in the
area surrounding the center pipe is to try to equalize itself by leaking
through the medium until the level is the same on either side of the
medium. Air would seep through the upper medium until the levels were
equal.

The above paragraph will only be true if the medium is so constructed as
to allow oil flow while not under pressure.

To test your hypothesis, next time I do an oil change, I will
specifically push the anti-drainback flap back with a tool so as to
break any vacuum that may be present, and see if oil begins seeping into
the center pipe.

 

but that's my point. the only way the center pipe won't refill is if
the filer medium is blocked to not just oil, but air as well, /or/ if
the one-way valve is not working and the filter is empty because it's
already drained. you've confirmed part of my original question, that
oem filters always seem to drain.

 

You have raised a good point here: I have never checked to see if the OEM
filter was actually full. Since the used OEM filters always felt as heavy
as the used aftermarket ones, I always assumed they were still full.

However...at times I've been in a hurry and have pulled the filter soon
enough that the center pipe was still full. This makes a hell of a mess and
makes me go through many paper towels mopping up the spills on the back of
the engine. I dump out what little there is left (if any) in the center
pipe and sit the filter down open-end up. And nothing seeps into the center
pipe. Not with OEM, anyway.

I'm a month away from the next change on either car, so stay tuned...

 

I cut open a couple of old filters after letting them stand to drain
for a while. The residual oil in there is just the amount that sat in
the relief valve area or could drain through the center tube.

The Purolator PureOne felt heavy, but if they stand upright for a
while I see oil seep into the center tube. So there is no restriction
in the media of my old filters to hold them from the center tube.

It's been a while with Honda OEM (Fram version or Bosch Filtech
version) when the owner gave the large filters. I only source
Purolator PureOne PL14459 or Bosch Filtech 3312. These are the "old"
large sized ones.

If smaller filters could work, while even the larger filters in the
first place?