5w20 vs 5w30

[Burla]

Makes you wonder why spec 0w40 for a hemi anyway, if we believe manu's actually do care about this you would have to think it is about oil companies making 0 winter rated oils their best effort oils. You see with Hemi395's latest uoa that 0w30 can have a higher viscosity at the end of an interval then 0w40's. So I really wonder why for the 6.4 they didn't spec a 5,10, or even 15w40 oil. What would be a better choice, 0w30 that has substantially less vii's then 0w40 and still ends up thicker at the end of the inetrval, or a 0w40 that's viscosity is all over the board? Between 0w40, 0w30, 5w30, 10w30, 5w40, 10w40, or 15w40, which would be the worse weight oil to lubricate a 6.4. I think one could actually make an argument 0w40 (just considering viscosity) is the worst choice of all of these options to lubricate a hemi.

 

[Burla]

Oops I thought it was the other thread, but here is my point, look at hammers viscosity after 4k miles with 0w40 pup. There are many choices to consider when you talk about viscosity, even the manu's choices have proven that other options are viable options when you look at and consider uoa's.

 

[GRN69CHV]

So I guess you still have the RAM then? You were talking about getting rid of it a few months I believe?

Yes, still have it. We decided to keep it when the company truck arrives. It's in really good shape, fully loaded. Just put a new battery in, only service left to do is new belt and trans service. It will be come a garage queen. I owe $$$ on it, but I couldn't buy anything close to what I have here for the amount owed .

 

[HEMIMANN]

Makes you wonder why spec 0w40 for a hemi anyway, if we believe manu's actually do care about this you would have to think it is about oil companies making 0 winter rated oils their best effort oils. You see with Hemi395's latest uoa that 0w30 can have a higher viscosity at the end of an interval then 0w40's. So I really wonder why for the 6.4 they didn't spec a 5,10, or even 15w40 oil. What would be a better choice, 0w30 that has substantially less vii's then 0w40 and still ends up thicker at the end of the inetrval, or a 0w40 that's viscosity is all over the board? Between 0w40, 0w30, 5w30, 10w30, 5w40, 10w40, or 15w40, which would be the worse weight oil to lubricate a 6.4. I think one could actually make an argument 0w40 (just considering viscosity) is the worst choice of all of these options to lubricate a hemi.

Absolutely. Looks like a marketing scam or ignorant grab to me.

 

[GRN69CHV]

Makes you wonder why spec 0w40 for a hemi anyway, if we believe manu's actually do care about this you would have to think it is about oil companies making 0 winter rated oils their best effort oils. You see with Hemi395's latest uoa that 0w30 can have a higher viscosity at the end of an interval then 0w40's. So I really wonder why for the 6.4 they didn't spec a 5,10, or even 15w40 oil. What would be a better choice, 0w30 that has substantially less vii's then 0w40 and still ends up thicker at the end of the inetrval, or a 0w40 that's viscosity is all over the board? Between 0w40, 0w30, 5w30, 10w30, 5w40, 10w40, or 15w40, which would be the worse weight oil to lubricate a 6.4. I think one could actually make an argument 0w40 (just considering viscosity) is the worst choice of all of these options to lubricate a hemi.

If someone were to do the search and ID the valve springs for a 5.7 or 6.4 truck engine and the Hi-Po 6.4 in the cars chassis, I would bet the valve springs have significantly higher seat and open pressure. Manufacturer most likely spec'd a lubricant for cold flow over the widest range of potential temperature variations to facilitate cold flow to the top end.

 

[Burla]

What has better cold flow, 5w30 or 0w40?

 

[Burla]

The colder it gets, the larger the differences. This isn't even that cold and you see 5w30 is better at cold flow then 0w40, at freezing temps the difference is huge.