I have researched the Valvoline Durablend MSDS sheets and found the 10w40 appears to be mostly Group II base oil along with the (Valvoline Techs tell me) 30 percent synthetic, which according to the MSDS must be Group III. This would make Durablend 10w40 a pretty good dino oil. Even better that the Durablend 15w40 as its MSDS indicates about 55 percent solvent dewax base oil or in other words apparently Group I mixed with the 30 percent Group III. Both meet ACEA A3 spec, but given the better base oil (apparently from the MSDSs) I am going to go with the 10w40. Also the 10w40 is easier to get and so can be found on sale (Pep Boys $1.99 first half of August with coupon). The MSDSs are at http://msds.ashland.com/
Just change the search for criteria to "contains" and enter Durablend.
Note the 5w20 and 5w30 Durablend both have high proportions of the Group II/III base,but the 10w30 and 20w50 (like the 15w40) are more heavily weighted to the Group I base oils. Appears the tighter spreads get the cheaper base oil here.
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