0w40 and 5w40 synthetics more shear stable than 10w40 synthetic?

[Ethan]

A recent oil thread on a bike forum to which I am a member of has brought forth the claim that this is in fact true. My knowledge is limited on the actual composition of the oil, so I'm turning to this borad to see if additional clarification is available.

Are 0w40 and 5w40 synthetics more shear stable than 10w40 synthetic?

To quote directly,

quote:

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In conventional motor oils VII (little polymers) are used to create the multi-viscosity span. These are what break and cause the oil to go out of grade.

10w40 contains a lot of these (AMSOIL's new $9 10w40 may not) regardless of synthetic or conventional. The synthetics should contain less.

With 0w40 and 5w40 can be accomplished very easily by the blending of different PAO basestocks with different viscosity indexs. Take a slightly thinner PAO oil and mix it with this PAO oil and BAM! 5w40. It's even easier when the spread is different (I believe AMSOILs 10w30 and 0w30 have no VII).

So 0w40 and 5w40 (and 15w40) have less or no VII to break. The 10w40s will still have a few.

The old rule of take 40 minus 10 to get a 30 "spread" as a gauge for shear stableness went out the window when synthetics came into the picture.

So it's the way the base oils are blended in synthetics that give it more shear stability (and lack of polymer VII). The addition of ester VII also helps the factor.

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Looking for more information,

Ethan

 

[DNS]

Every thing else being equal, no. A 10W40 synthetic can be obtained by blending base stocks of different viscosity just like for 0W40 or 5W40. However, you can't generally get that kind of viscosity spread without a little bit of viscosity improvers. The 0W40 and 5W40 because of their greater viscosity spread actually require more viscosity improvers than the 10W40 (assuming the same quality of basestocks).

As far as I know, it's impossible to get an 0W40 or 5W40 conventional oil without significant amounts of viscosity improver.

Now, if you're comparing a conventional 10W40 to a synthetic 0W40 or 5W40, the conventional oil will need much more viscosity improver than the synthetic but that is duew to the difference of base stocks not 0W40 or 5W40 vs. 10W40

 

[nicrfe1370]

That statement from the "guru" on the other board is so far off base it makes my head hurt. Just like DNS said, if you can mix different oils and get a 0W-40 or 5W-40, then you can even more easily mix oils and get a 10W-40. I'm just stupified by his pretend knowledge.

 

[Mickey_M]

quote:

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Ethan:

..... Are 0w40 and 5w40 synthetics more shear stable than 10w40 synthetic? ......

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As an example, ExxonMobil's Mobil 1 MX4T 10W-40 is specifically formulated for motorcycle use and is extremely shear resistant.

The oil is formulated by using a dumbbell blend of two PAO bases stocks, a trace of very stable VI booster, and contains very high additive levels.


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[wileyE]

My own unscientific experience using 5w40 vs 15w40 of the same brand (rotella) in a shared transmission MC is that the shifting degrades sooner with the 5w40.

 

[Juan]

i've read on this forum, or maybe others, that the synthetic 40 wts. pour easily and need very little pour point depressants to meet the 5W specification. Please correct me if I'm wrong.

 

[DNS]

quote:

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Originally posted by wileyE:
My own unscientific experience using 5w40 vs 15w40 of the same brand (rotella) in a shared transmission MC is that the shifting degrades sooner with the 5w40.

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Maybe that's true with Rotella, but in my bikes I've found that Mobil Delvac 1 shifts smoother than any other oil I've tried and with little or no degradation of shifting over the OCI.