Shell Spirax 80w-90?

Any one ever used Shell Spirax?
I work in a plant that goes through ridiculous amounts of Spirax 80w-90.
I've asked my Boss what we pay for it. He says it's pretty cheap, and that he could put some money into the slush fund in trade, but didn't specify a price.
Is this Spirax any good, or is it a cheap oil since it gets changed out all the time anyways?
I live on the West Coast of Canada, so it does get fairly cold (-10c or so)for a few weeks a year, but other than the odd cold-snap it generally stays around freezing... Would the 80w still be too heavy?
Is this worth the savings? Or am I going to regret my cheap-out when winter rolls around?
I don't see the point in paying the stealership for their over-priced stuff if it's not worth it, but can afford to buy some 75w if it's going to be worth the money.

Also, I see some guys here saying to put 75w-140 in their rears, is that a good idea for weekend off roading, or more for the serious builds?

Cheers, and thanks for any input

 

Compromised integrity cost a lot more than $20 bucks at the parts store. The weight is fine. How about you just ask your boss if you could have 3 qts if you really need it.

 

I stand corrected, and admire your integrity.
Edited my original post after asking the boss man about it. Thinking I should just pay up the money for better quality oil, since it's likely worth it.
Still not forking out for the Toyota brand stuff though, just for oil filters...

 

Cool.
Only Toyota fluid you should run is their WS ATF. I like the oem filters too. Cheap and higher quality than most after market.

 

For the record: I changed all my gear oil with Lucas several months ago at work. My boss showed up in his 70's Ford and was giving me a hard time about my truck running on synthetics, saying that if had an older one that I could get away with just using the gear oil from work...
Still glad i went with a high quality synthetic, but might have been smart to run some free oil in the front diff for a few months before changing over to synthetic as it was full of shavings. No problems engaging it, and I blew out as much of the junk as I could with compressed air.
I'm thinking the previous owner only ever got around to changing out the rear and the transfer case as they were still nice and clean.