RL 5W-40 all year or 10W-40 in (very-hot) summers?

[harrydog]

Where have you read that Redline uses no VII's in their 5w40? I've not heard that anywhere.

 

[Jeffrey Behr]

I am the source for the Red Line Viscosity-Index-Improver info, and Red Line is my source. Dave Granquist told me in writing that the 5W-40 is the only RL oil that uses any VIIs.

I'll be using RL 10W-40 in our very-hot summers and 5W-40 in nonsummers, changing each 6 months at what will be c. 11,000 miles. (Porsche recommends 20,000-mile intervals.)

 

[Jeffrey Behr]

quote:

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Originally posted by Jason8691:
Then I stand corrected, I thought I read that in one of their info sheets. But after about an hour of looking I gave up! Thank you Jeff Behr, do you know why they use them in the 5W40 and none of the others?

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I believe it's because their warm-5W base oil doesn't have quite the viscosity index to make it to the hot-40-vis range. Think of the 5W-40 as 5W-30 PLUS a little VIIs so it doesn't thin as much as the hot-30 does at 100°C.

(Understand--I didn't say RL 5W-40 is the same as their 5W-30 with VIIs added, I suggested you think of it as the same.)