5w-30 high mileage or regular 5w-30 question

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623
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Pullman Wa
Will one of the high mileage 5w-30's have a better chance of holding it's viscosity over a conventional 5w-30? I'm talking over a 3,000-4000 OCI. I know regular Maxlife is part synthetic so I figued the 5w-30 might hold it's viscosity.
 
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8,937
Location
SC
Quote:
Will one of the high mileage 5w-30's have a better chance of holding it's viscosity over a conventional 5w-30?
Yes. Because HM oils are typically blended on the thick side, they will hold their vis better. Take a look at my recent UOA on Castrol GTX HM 5w30. It was in use 14 months and 4000 miles but was still 11.2 cST, which is a solid 30wt. Most regular 5w30s will drop into the 20wt range over their service life.
 
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8,937
Location
SC
Quote:
...and then start climbing again from oxidation breakdown byproducts - which may've happened in your case. Just a thought.
Not according to the numbers. Oxidation was very low, thanks to LC. The oil did shear some. GTX HM 5w30 starts out around 12, I think.
 
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1,574
Location
Alamo, CA
The 5-30 and 5-30 HM shear about the same. The HM starts at a higher vis and drops about the same amount of vis as the 5-30 but stays in the 30 range. If you want to stay 30 over your OCI and don't need the sealers, you could just add 1 or 2 qts 10-40 to 5-30 or just use 10-30.
 
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