The AC2 treated lumber I built my porch with was heavy and "wet" when I bought it a few months ago. Porch is up and been "drying" for about a month now. How long should I wait before applying a oil based stain/sealant ? Is there a way to test the wood ? thanks

6 months is what I tell customers
A year is better
Don't forget to pressure wash it clean and let it dry before you strain it

I built a fence out of treated and was told to wait a year before painting or staining.

Curious if you or anyone else knows if staining treated lumber will help preserve it or if the treated is good enough for long term?

Used motor oil is the traditional deck stain around here

I'd definitely wait a year or so.

I was told at a bare minimum wait until the water no longer beads on new lumber , and then wait some more.
One year here for me.

I have replaced/repaired foundations that were below grade......built of pressure treated material. I think the oldest was 25-30 years old. The wood was in pretty good shape but almost all of the fasteners had rusted away. The only thing holding the structure together was compression.

Wait a year before applying anything.

at least a year and thats not a cold wet year either i dont think they call it pressure treated anymore either last treated dimension lumber i bought wasn't even rated for ground contact

Should be stamped "ground contact"

we wait a year here.

Does being marked " kiln dried " matter ? either way , saves me some work this year.

I believe it all gets kiln dried prior to being treated, some companies also offer kiln dry lumber after treatment as well. I've never used it, but I'm guessing that's not what you're working with as it wouldn't be wet and heavy as you described.

Drip water on it. If it soaks in within 10 minutes, it’s ready to stain. If it still beads up wait

What happens if you stain it or paint it a week after you build something?

If using a clear type preserver----right away. I did mine as soon as I was done building it back in 2004 with CWF flood clear. Hold up fine. No peeling and retained the honey color of the wood.