5w40

[boxcomp]

I was reading a thread on here about how 10w40 used a lot of VI's and breaks down and leaves deposits. Is the same true for a synthetic 5w40 such as the Rotella T I just bought?

 

[cweed]

synthetic oil has a naturally occurring high vi, thus it does not need as much vii as dino oils, so a good quality synth 5w-40 will need very little vii, unlike a dino 10w-40, good example of this is rl 5w-40 vs pep boys brand dino 10w-40

 

[Palut]

From what I've learned here: Stay away from large viscosity spreads in dino oil, don't worry about spreads in synthetic unless they're huge.

 

[Jelly]

quote:

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Originally posted by boxcomp: I was reading a thread on here about how 10w40 used a lot of VI's and breaks down and leaves deposits. Is the same true for a synthetic 5w40 such as the Rotella T I just bought?

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A lower quality base oil combined with a wide spread results in an oil that will most likely sheardown a bit resulting in all sorts of "good" things... Rotella 5w-40 is a group III 5w-40, and as such does have an amount of VII's in the mix, BUT it uses a very high quality base oil in conjuction with VII's that are very carefully selected (given it's an HDEO)

quote:

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Originally posted by Palut: From what I've learned here: Stay away from large viscosity spreads in dino oil

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What defines "large"? Would 15w-40 be "large"? I take it you wouldn't approve of 25w-70?

 

[Palut]

quote:

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Originally posted by Jelly:

quote:

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Originally posted by Palut: From what I've learned here: Stay away from large viscosity spreads in dino oil

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What defines "large"? Would 15w-40 be "large"? I take it you wouldn't approve of 25w-70?

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I would define more than 30 points as large for a dino, and more than 40 or 45 large for synthetic. But I really have no experience with large spread synthetics, so I could be very mistaken. If I am, please let me know!