Until today, I thought oil expander rings were ALL non-directional.

I noticed a ring manufacturer indicate that on their piston ring set instructions that the oil expander (the bottom wavy ring) is indeed directional. This really surprised me.

The issue is where the ENDS come TOGETHER.

In searching online, I've found two diagrams showing the opposite recommendation of each other.






I know, I know, just follow the directions...

But what is the thought behind this? If you install a compression ring upside down it will push oil towards the combustion chamber, a big goof, but what about the expander ring installed upside down?

Any thoughts or explanations?

maybe the expanders just provide tension to the oil rings & do not affect oil consumption

It is NOT MAYBE, they only apply pressure to the scraper rings
BUT, if your brand rings instructions say install them with the ends pointing down do it that way
I've install many different brands of rings in a lot of different motors and I have not seen any instructions like you found on the interweb
I'm sure I've installed them both ways with that type of oil ring spacer with no bad results
I do make sure the ends do not overlap and or pile on top of each other

I'm with you Cab, never seen this before.

I'm looking at the paper install instructions from Hastings for this basic ring set and it says "Caution: 2mm oil ring install with gap towards top of piston".

I just follow instructions but it makes me wonder how critical this is in reality.

Manufacturers are not going to waste their time, money and ink on putting special instructions with their products unless it is needed, badly.
Follow them, I will

I'm not so sure. If the tech line keeps getting calls about "do the ends point up or down", the smart manufacturer will choose one or the other, knowing all the while it doesn't make any difference, just to answer the question.

The expanders I've seen do not contact the cylinder wall and are basically symmetrical with no discernible top or bottom except for the ends. I don't see how installing them up vs down would make a difference.

That being said, I've never seen the direction of installation spelled out in any instructions. If it had been, I would follow the manufactures directions.

You're right, they're absolutely symmetrical, except for where the ends come together- They form an arrow of sorts. I'm wondering if when traveling in one direction the expander ring functions better / as intended when that arrow shape may begin to separate and form a gap, pushing out. In the opposite direction the end gap closes. That's the only thing I can think of.

They function the same regardless of orientation, but seen once where the gap in the rail and the tip lined up, and the tip slipped down in an oil drainback groove and stuck.