Is PP 5W-20 as sheer stable as PP 5W-30?

[Tucson Five-O]

Good evening fellow BITOGERS

I want to use PP in my 2008 Impala with the 3.5L Flex-Fuel V-6.

I've used the Chevron 5W-30 dino with great results. It, along with PYB are my two favorite dinos. I like the thin 9.7 cst @ 100C viscosity of Chevron. I presume it probably has an HT/HS of 2.9 which is the minimum allowed for an oil to be called 5W-30.

I know the PP 5W-30 is 10.3cst @100c. I would like to blend it with PP 5W-20 (2/3 10.3 + 1/3 8.48) to get approx. 9.7.

I know that the 5W-30 has GM4718M & HTO-06 certifications for Corvette and Acura.

Do you think the 5W-20 is as sheer stable and deposit resistant even though it has not been certified as such (since Corvette, although I have heard that will change in the next couple of years, and Acura do not spec the 5W-20 oils in their performance applications)?

I think that oil for oil, Mobil1 5W-20 is more stable than 5W-30 and Mobil1 EP 5W-20 is even more stable than their 5W-30 counterpart, etc. or is that not necessarily true due to blending differences, such as the 5W-30 having, say, more PAO in the mix?

Any insight would be appreciated, and yes I know that running PP 5W-30 would be fine as well.

Thanks,
Gary

 

[tig1]

I did one UOA last Jan. in the Focus at almost 10,000 miles and it was very stable. SUS vis @ 210F 59.8, and cSt Vis @100C 10.15 with the M1 5-30EP. Right in the middle. Engine remains very quite with this oil.

 

[Tucson Five-O]

tig1,

I know that M1 5-30EP is very stable as is PP 5-30 (I wasn't intending to compare the two. I believe that M1 EP will allow longer OCIs). I was just wondering the effect on shear stability and high temperature deposit resistance when PP 5w-30 is "diluted" by PP 5w-20 by 1/3.

Gary

 

[Drivebelt]

I would be pretty sure the PP 5W-20 is as good an oil as the 5W-30 from a base oil and VII perspective.

5W-20's (all things being equal) should be more shear stable than a 5W-30 as they will use less VII (viscosity-index-improvers).

Personally, I don't see enough of a difference between 10.3 and 9.7 to quibble about.

But, if your heart is set on 9.7 cSt

... ... well mix away.

 

[Gary Allan]

Without addressing all of your detailed points, I agree with Drivebelt.

Flexblending is not only a tradition here on BITOG, it's more or less a rite of passage.