So... is GC really so shear stable?

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Mar 1, 2003
Fairfield County, CT
Check this out; let me know if I've made any errors... For the first two cars I'm using a VOA viscosity of 65.9 (which is the average of 65.8, 65.8, 65.9, and 66.2, gathered from 4 Blackstone virgin reports) And for the third (Patman's sister's car) I'm using Patman's VOA viscosity of 12.2. Patman, are those viscosities from the same lab? (Wearcheck?)
car                 miles    UOA visc  %visc loss
Toyota Sienna       4648      62.0        5.9
Honda Civic b16a    5279      62.8        4.7
Honda Civic         5500      11.5        5.7

Hmmm... [ October 06, 2003, 10:49 PM: Message edited by: quadrun1 ]
The only way to really judge is to compare the VOA vis of the SAME oil you're doing the UOA on, not an average vis from a bunch of different VOAs. We'll be finding out how well this oil has held up in my Chrysler shortly. FWIW, I think any multigrade oil is going to shear some. "Shear stability" is a relative thing, and relatively speaking, the GC seems to be shear stable.
Yes, both the virgin sample I sent and the UOA on my sister's car were from Wearcheck. The one thing though is that the oil I put in my sister's car was from a different batch than the VOA oil, so it is possible her oil was slightly different in viscosity. Also remember, it was her first run with GC, so there is a little bit of the thinner M1 mixed in there. Her second UOA (which I'll have in a couple of weeks) will be the better one to see for viscosity. And my own UOA (due next week) will be good too, since before I put in the GC I have now, I ran a 3L rinse cycle to try and get close to 100% GC in my engine for this run. And the batch in my car is the same as the VOA too.
Originally posted by Eiron: How 'bout these shear numbers I figured a few weeks ago? Or these recalculated shear numbers I figured the next day? (I threw out the worst example.) Yes, I'd say EC 0W-30 looks very good too. Almost as good as M1 0W-40 ... [Wink]
Eiron, You just don't give up do you? [Big Grin] Well, neither do "we," so here's to healthy and collegial competition. [Cheers!] [ October 07, 2003, 01:08 PM: Message edited by: pscholte ]
There are some good M1 numbers too! M1 0W-40 in G-Man's Olds minivan (4200 miles) thinned only about 1% After 5,000 miles in an Audi S4 twin-turbo and also after 5K in an Audi 1.8T, M1 0W-40 thinned about 6%. In the S4, the M1 0W-40 wear numbers were about that same as Amsoil S2K. I think it's a close call, these are both very good oils!
What we really need to see is someone run 2 intervals with 0w40 M1, then two intervals with GC 0w30, in the same engine, in order to see the behavior of the two.
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