Do all xw-30 dino oils shear to 20wt??

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Oct 24, 2002
west central missouri
Last two UOA's done on my wifes Maxima have sheared down to 20wt within 3k. Is this a given or are there xw-30's (OTC dino)out there that will stay in grade for 3k?? I've noticed the "High Mileage" oils start at a higher 30wt,is this the best option?? By the way, the oils mentioned above were Tropartic 10w-30 and Castrol 5w-30.Any ideas?? [I dont know]
I think the high mileage oils are going to be more stable due to the addition of esters in the base oil. Plus their thicker viscosity to begin with means it won't thin out to a 20wt as well. When I ran the 10w30 Maxlife in my car it seemed to hold it's viscosity extremely well. The first 2400 mile UOA I posted showed the viscosity at 11.4, and the second UOA, at 3300 miles, showed it at 11.5. So it appears to stay pretty constant. I'm not sure on the 5w30 versions though. We'll see at the end of this year when I do a UOA on the 5w30 GTX High Mileage I'll be running in my mom's car. For the slight price difference between the conventionals, and their high mileage versions, I think the high mileage versions are a better choice.
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