80W 90 is fine. Do they maintain their level?

The older Ariens SnoThros specified their Liquid Grease,a NLGI #00 Lithium EP grease. Probably available at other places- I don't know how much it costs at the dealer. I believe the lower plug is the overflow, the top plug is the fill.
One of the problems is getting the "semi-fluid" grease to flow into the housing, especially in cold weather. The Ariens manual suggests placing the SnoThro in a warm area to allow the unit warm up. I would also allow the grease to warm up.
From what I understand, the older housings have gaskets that might allow gear oil to weep out. Later housings have a sealant between the halves, so a gear oil might be OK.
I would confirm by downloading the manual from the Ariens website. Click on Customer Service, then enter the model and serial number of your auger half.
Good Luck
Ralph

Thanks Tom P. I have no clue, I havent looked. I actually have bits and pieces of 4 similar old Ariens. Last Sunday, I picked up another one that I got running with a carb from HM60 on the 24" with a bad augur shaft. I will pop the fill plug and check it the morning. I can get gear oil locally, If it was some proprietary goop, I would have to travel further afield and deal with kid who wasnt even born when these things were made.

I don't think these boxes are fussy. Areins has had several specs, like most. Some specified #2 lithium, some 90, some 00. I've seen 00 used, but mainly gear oil. If what seems to be in your box is not grease, but not totally liquid like gear oil- then you likely have 00. I don't like mixing lubes, so the easiest answer to the question is to try and match what you have.
When they leak, you basically have the choice to pull it apart, correct the seals, bushings etc or drain it over night and pump it full of #2 lithium if you want. Some guys even put bentonite in them. In the shop if you have a thrower and it becomes the choice of doing major damage just getting it apart, or putting in the heavier lube. They seem to not know the difference in lube- as long as it isn't lackolube...

I'm draining it now after a 10 minute warm up. Gear oil with water in it is what is coming out. Darn little of it. I bought a qt of 80-90, so, right or wrong, that is what it is gonna get.