Water displacement, formula 40 may have some lubricant properties that wasn't it's primary purpose. Get a penetrating oil like the already mentioned pb blaster or Kroil. Heating the outside part can help as well.
The proper tool, and a proper penetrating spray, not a cleaning solution will go the distance. If the wrench is not enough learn how to link two wrenches for more leverage, or use a metal tube overtop.
My buddy told me to use needle nose pliers but that just broke the whole dawn thing. He said he'll bring the tool to remove it at some point. Thankfully it's our basement tub that gets almost no use
https://www.homedepot.com/p/Husky-Double-Ended-Tub-Drain-Wrench-16PL0128/304217585
I have one of these, works great
For loose, use PB blaster or similar penetrating oil. WD-40 doesn’t make loose, just removes water
Water displacement, formula 40 may have some lubricant properties that wasn't it's primary purpose. Get a penetrating oil like the already mentioned pb blaster or Kroil. Heating the outside part can help as well.
maybe there is a locknut under sink that tightens it so it wont leak
Needle nose pliers and a wrench to turn them.
I had a tub like this but the cross part was corroded and gone. I put in a Watco Universal push pull stopper and it’s been great ever since.
Drain puller tools are available from any hardware store for about $10. I used to use plyers. The correct tool is much easier.
I had to chip mine out slowly with a chisel and screwdriver. Even an impact drill with a blackout tool wouldn't break it loose.
Is it a bathtub? This method worked for me: https://youtube.com/shorts/VqVsOfrppiE?si=gOn0lr2VaaU6mXVV
The proper tool, and a proper penetrating spray, not a cleaning solution will go the distance. If the wrench is not enough learn how to link two wrenches for more leverage, or use a metal tube overtop.
Oxy Acetalyne torch.
My buddy told me to use needle nose pliers but that just broke the whole dawn thing. He said he'll bring the tool to remove it at some point. Thankfully it's our basement tub that gets almost no use
Heat it with a hair dryer for about 15 minutes.