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Lubrication question

This is not strictly car-related, but I think that it does relate… at least to some extent.

When servicing my snowblower, I noticed that the augur drive was a bit low on oil.
So, I consulted the manufacturer’s manual to make sure that I bought the correct viscosity gear oil.
It noted that 80w-90 oil should be used, but it additionally stated… DO NOT use synthetic oil!
Does anyone have an idea why synthetic oil is a no-no with that gear drive?

My guess is some synthetic base stocks are incompatible with the seals.

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I never felt the need to lubricate the auger gear on my MTD 2 stage snowblower.My owner’s manual doesn’t mentioned when to service it or what type of oil to use. My guess is that it is lubed for life but I doubt it.

This will be my third winter with this Toro 2-stage model, and I never gave the augur oil any thought until a few days ago when I was changing the engine oil. That was when I noticed the info in the manual regarding the augur gear lube, and–sure enough–it was a little low.

Here’s what one website says. Maybe that application results in an unusual amount of varnish-forming byproducts.

"Most gear oils use a polyalphaolefin (PAO) as a base stock. This is essentially a man-made version of the naturally occurring mineral oil pulled from the earth and refined. The size of the molecules are all relatively the same. These are also saturated molecules, which makes them very stable.

The benefits of synthetic oils relate to the molecules’ stable nature and include a higher degree of hydrolytic stability and demulsibility, a higher viscosity index (VI) and a lower pour point. The VI and pour point allow these oils to perform better across a broader temperature range.

The drawbacks of synthetic oils would include their cost and solubility concerns. PAOs generally have low solubility, which means they do not dissolve additives as readily as their mineral counterparts. Synthetic oils also have a difficult time suspending varnish-forming degradation byproducts."

Is it possible that the additives in the synthetic oil are too strong for this application?

I work on elderly motor scooters that usually have no oil filter, only a screen. Because of that the ability of synthetic oils to carry “dirt” in suspension, so it would be filtered out if there was a filter, increases the wear on engine parts. The dirt settles to the bottom of the crankcase very slowly, and stays up in the system. Gear oil is not generally filtered so maybe that’s why dinosaur oil is recommended.

And maybe I’m nuts, but I’m sticking with it until I’m proven wrong.

I refilled my gearcase once om my 8 hp Airens snow thrower. Maybe I should check it again, it is a 1972 model and it was marketed back then as a Sno-Thrower attachment for a 2 wheeled garden tractor. You could also get a roto-tiller attachment and a sickle bar mower.

i replaced auger gear in my blower. there was only grease inside case