I think we need to keep in mind what "enough" protection really is. I liked what dagmando said in another thread, about the difference between when we think an oil is trashed based on hyper-scrutiny of UOAs, & when it really is trashed to the point where it's no longer providing enough protection. If we start out with 5x more protection than "enough," & we degrade down to 1x or 2x more than "enough," then why are we concerned? Why do you want to throw out your oil if it still has 3x or 4x more protection than you need? To look at it another way, do you replace tires & brakes when they're only half way thru their lifespans? These are life-saving components, but how many of us wait until the tires reach the wear bars, or the brakes squeal against the wear indicators before replacing them?
I guess I'm also trying to reconcile the implications that a thick 30wt is an "extra effort" by a manufacturer, while a thin 40wt is a "weak attempt" by another. What I mean is, it takes more effort to go those few extra cSt points, & then it's simply a classification technicality which separates the two. They're all just points along a sliding scale, divided up for a buying public which is "too dumb" to know what the numbers mean, right?
Jay, I think they run the oil thru an injector to accelerate the shearing, since it would take so long otherwise.
RobY & Terry, while I agree with Terry that price is a necessary factor in product developement decisions (we couldn't afford cars otherwise), I also agree with RobY in his assessment of manufacturer's oil choice in this case. A car maker using 0W-40 is saying, "We choose an oil which is only possible as a fully synthetic variety." The owner can't get the car home & say, "Hmmm, I think this T-Rex Brand 0W-40 conventional oil will work just as well as their UberStrasse Brand full syn," because you can't get a 0W-40 in a dino oil. Also, I would think Mobil has other, less expensive (ie, higher volume) full syns for a manufacturer to use if price were the main deciding factor.
Ted, I'm really curious to see what it does after 10k miles. The Tacoma did exactly as you'd expect, shearing & then thickening back up. But Pablo's S2k 20W-50 kept shearing, & now nicrfe1370's S2k 20W-50 post seems to show the same trend with only half the miles. This is one of the better oils available, at $9.05/qt, & only has a 30 pt vis spread. I'm wondering if my Saab turbo will continue to pummel the oil like the Volvo & Subaru turbos did.
palmerwmd, as others have said, I'd like to reduce my costs & time spent doing oil changes. If there's an oil that will help me in this, I'm interested. It's the same reason why people buy power tools, dishwashers & microwave ovens: it's cheaper & easier in the long run. But the biggest reason for me was conservation of resources. Sure, I hated the inconvenience of having to change the oil in one of the cars every 6 weeks, but all the waste was just killing me.
Bill J, I think you're right, & I'd like to see more UOAs on 8k-12k mile intervals for some of the low-spread (20-30 pt), higher HT/HS (WAG: above 3.3?) oils. My questions are similar, in that I'm curious how well an oil's protecting if it starts its thickening cycle very early in its lifespan, or if it doesn't thicken at all during an extended interval.
Thanks to all for the thoughts & comments.
