Yellow metal safe gear oil

[LoneRanger]

It might have been their motor oil I saw, I am sorry.

 

[Oblithian]

Is there any easy way to tell which gear oil is yellow metal safe. I am looking for 80w90 to put in a tractor, and I can't tell which ones are safe and what isn't.
Most do not seem to say either way, does anyone have a list?
I can't afford expensive synthetic, just conventional from an "off the shelf" supplier. Possibly the Napa branded Ashland stuff? Tractor holds 5 gallons, so i have to watch the budget.

There is a test for yellow metal safety:

This thread has more information on yellow metal safe/ non-corrosive gear oils: https://bobistheoilguy.com/forums/threads/copper-strip-tarnish-test-10-gear-trans-fluids.171491/

It should make things easier for the people looking for answers to be funneled there.