Rear gear oil

I did a search for this but nothing came up.... I have a 79 KZ1000ST. The diff says to put 90W in it for temps above 41 degrees F, and 80W for temps below 41. All i can find at the auto parts stores is 80W90, I assume this would be just fine, but figured I'd double check on here. Any input? Thanks!

-Phil

-PS i wasn't sure if this belonged in here or the engine section, if it's in the wrong place i apologize!

80w90 will work just fine

Thanks! changed the rear oil today and used 80w-90!