Is there really that big of a difference in quality between these two oil types? Yamalube is $40 / gallon while Supertech is $8.

Where is Yamalube $40/gal.? I want to say I pay $24ish. I heard that Wal-Mart oil is good stuff too. Many oils are actually the same exact stuff...just different wrapper. I used to work at a bottleing facility for many types of oils. I know for a fact that at one time Ford Motorcraft & Meijer oil was the exact same...just a different label. They may spec out different requirements over time, but very few private labels actually have their own patented formula. If you had the $$, you could have your own brand of oil too.

I don't know for sure specifically about the WM brand, but I know peeps who run it & have no complaints...marketing is everything. Don't think because it's cheap it's not good. In reality it could be the same as a $25/gal oil in a different package...naturally you want to go the one that costs more because it must be better...welcome the world of marketing.

A tech told me its all in the additives..It's the additives that cost money..It may be it's all bottled the same but don't count on it...

I'd look around and find the best price on YamiLube.. or get some buddys and chip in and buy in bulk.. We bought a 50gal. drum of Merc oil once.