GM permitting 0w20 in 5w20 cars

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Originally Posted By: ExMachina
Making a 0w-20, you start with a thinner basestock oil compared to a 5w-20, and the 0w-20 will drop in hot viscosity over time sooner than the 5w-20 since the 0w-20 relies on VII polymers more. This varies some with what oil, GroupII or GroupIII,IV etc we compare, but in general Honda got nervous about what might/could/does happen in some of their high-performance engines especially. GM does not look as nervous about it.

Chevron Oronite's website says it best: "The oil’s viscosity falls during the test due to polymer coil breakage. In other words, only that part of the oil’s viscosity which is contributed by the VII polymer is susceptible to breakage. Neither the base oil nor the additive performance package suffers permanent viscosity loss. Moreover, different VII polymers have different shear stability characteristics, depending on the molecular weight and chemical nature of each. Those VIIs having higher molecular weight have a greater propensity for polymer coil breakage.

A VII polymer’s “Shear Stability Index” (SSI) is defined as its resistance to mechanical degradation (polymer coil breakage) under shearing stress.

Example: An oil is formulated with base oil of viscosity 5 cSt and a VII is used to increase its viscosity to 15 cSt. The VII’s viscosity contribution is therefore 10 cSt. During the shear test, the oil’s viscosity falls to 12 cSt. It has permanently lost 3 cSt of viscosity.

VIIs are available across a range of the SSI and oil formulators choose the appropriate VII product that allows them to meet their finished oil performance and marketing needs.
"

Making a 0w-20, you start with a thinner basestock oil compared to a 5w-20, and the 0w-20 will drop in hot viscosity over time sooner than the 5w-20 since the 0w-20 relies on VII polymers more. This varies some with what oil, GroupII or GroupIII,IV etc we compare, but in general Honda got nervous about what might/could/does happen in some of their high-performance engines especially. GM does not look as nervous about it.


Except that this may not be the case because you are comparing a synthetic (0w-20) to a conventional (5w-20) which may actually be using MORE polymer than the 0w-20. Now synthetic to synthetic? Sure, that's like the case.

Member bobbydevro noted that one of his "favourite" oils was a 0w-20 blended with no VII's in one of our past discussions, which I thought was pretty neat. Just leveraging PAO as the base.
 
Originally Posted By: OVERKILL

Except that this may not be the case because you are comparing a synthetic (0w-20) to a conventional (5w-20) which may actually be using MORE polymer than the 0w-20. Now synthetic to synthetic? Sure, that's like the case.


That's why I said this:
Originally Posted By: ExMachina
This varies some with what oil, GroupII or GroupIII,IV etc we compare, but in general Honda got nervous about what might/could/does happen in some of their high-performance engines especially. GM does not look as nervous about it.


The subject of this thread is what engine makers are recommending as guides, and of course that can't take into account all the different possibilities, so they err on the side of caution (Honda for sure).
 
Originally Posted By: ExMachina
Originally Posted By: OVERKILL

Except that this may not be the case because you are comparing a synthetic (0w-20) to a conventional (5w-20) which may actually be using MORE polymer than the 0w-20. Now synthetic to synthetic? Sure, that's like the case.


That's why I said this:
Originally Posted By: ExMachina
This varies some with what oil, GroupII or GroupIII,IV etc we compare, but in general Honda got nervous about what might/could/does happen in some of their high-performance engines especially. GM does not look as nervous about it.


The subject of this thread is what engine makers are recommending as guides, and of course that can't take into account all the different possibilities, so they err on the side of caution (Honda for sure).


Fair enough. Honda also spec'd 10w-30 (because they were spec'ing conventional across the board back then) for the S2000 due to its shear stability. However, they also mention in the owners manual that you can use 5w-40 (which would be synthetic) if you are anticipating cold temperatures.

IMHO, these are the obstacles one has to deal with when you aren't requiring your own oil spec's. GM with DEXOS can now require that 0w-20 to be DEXOS approved, which guarantees a GM-verified level of performance, similar to what BMW, Mercedes, Audi, VW....etc do.
 
Originally Posted By: OVERKILL

IMHO, these are the obstacles one has to deal with when you aren't requiring your own oil spec's. GM with DEXOS can now require that 0w-20 to be DEXOS approved, which guarantees a GM-verified level of performance, similar to what BMW, Mercedes, Audi, VW....etc do.

OK, I was thinking the same thing. GM's dexos1 spec (all small letters please) has more shear testing so the oils are up to par anyway, making GM more open about going to 0w-20. I guess Honda could just recommend dexos1 ???? Ha! They should.
 
Originally Posted By: ExMachina
Originally Posted By: OVERKILL

IMHO, these are the obstacles one has to deal with when you aren't requiring your own oil spec's. GM with DEXOS can now require that 0w-20 to be DEXOS approved, which guarantees a GM-verified level of performance, similar to what BMW, Mercedes, Audi, VW....etc do.

OK, I was thinking the same thing. GM's dexos1 spec (all small letters please) has more shear testing so the oils are up to par anyway, making GM more open about going to 0w-20. I guess Honda could just recommend dexos1 ???? Ha! They should.


I'm not a fan of lower case for a "name"
wink.gif
So I misspell it on purpose, LOL!!

That'd be hilarious if they did spec the GM DEXOS 1 spec
grin.gif


Honda DID come up with HTO-06, not sure why they shy away with more generic specs like the others come up with
21.gif
 
Originally Posted By: OVERKILL
Fair enough. Honda also spec'd 10w-30 (because they were spec'ing conventional across the board back then) for the S2000 due to its shear stability. However, they also mention in the owners manual that you can use 5w-40 (which would be synthetic) if you are anticipating cold temperatures.

The first 4 years Honda didn't recommend 5W40 for temperature below 0F, only starting 2004 Honda did that.

One question, why Honda recommended a thick 5W40 instead of synthetic 5W30 or 0W30 for colder climate ?

Some S2000 AP1 owners actually use 0W40 and 5W40 in summer when they track their cars. Their reasoning is if 5W40 is usable for temperature below 0F then it should be okay for 90-100F or higher.

Since I never encounter temperature below 30F, 10W30 is what I use.
 
Originally Posted By: HTSS_TR
Originally Posted By: OVERKILL
Fair enough. Honda also spec'd 10w-30 (because they were spec'ing conventional across the board back then) for the S2000 due to its shear stability. However, they also mention in the owners manual that you can use 5w-40 (which would be synthetic) if you are anticipating cold temperatures.

The first 4 years Honda didn't recommend 5W40 for temperature below 0F, only starting 2004 Honda did that.

One question, why Honda recommended a thick 5W40 instead of synthetic 5W30 or 0W30 for colder climate ?


Because it is kind of a synthetic "spec" by proxy without saying it IMHO. If they spec'd a 5w-30, they'd have to call for a "synthetic" (which also may still be shear prone) whilst if they call for a 5w-40, they are all synthetic anyways. The 0w-30 perhaps didn't exist at that point in time? I think the only available one was GC.

Originally Posted By: HTSS_TR
Some S2000 AP1 owners actually use 0W40 and 5W40 in summer when they track their cars. Their reasoning is if 5W40 is usable for temperature below 0F then it should be okay for 90-100F or higher.

Since I never encounter temperature below 30F, 10W30 is what I use.


Yes, the 5w-40 and the 0w-40 would be fine, as they have the guarantee of a certain amount of shear stability based on the Euro and/or HDEO specs they meet.

I feel that Honda just really likes to spec "generic" oil whenever they can. It is easy and fits with the "low maintenance" image, just like Toyota. The RDX was I think the only exception to that.

On the other hand, the Euros, because of their "prestigious" image, it is fitting that they have "specific" oil requirements.
 
Originally Posted By: OVERKILL
That'd be hilarious if they did spec the GM DEXOS 1 spec
grin.gif


Infiniti/Nissan specifies Dexron-VI for their power steering, and other Dex stuff earlier on.
wink.gif
I guess there's a precedent!
 
Originally Posted By: camrydriver111
Is 10W30 not thick enough for the S2000?


It is, most certainly, but the problem came with the cold weather spec.

As per BITOG lore, 5W30 conventionals always became 5W20s, and Honda appear not to have desired that to happen.

So by starting at a 5W40, they got the cold weather performance, and still hot protection, and greater buffer if it DID shear some.
 
I actually used various dino 10W30 the first 12-13 years of ownership of the S2000. The last 2 years I mixed 3 quarts M1(and Castrol) 0W40 with 2 quarts 0W20 to get HTHS of around 3.4-3.5. Performance wise I didn't feel any difference when accelerated to 7-8k RPM compare with dino 10W30 with 3.0-3.1 HTHS.

If the mixed shears down a little in 5k/12mo OCI, it still is above 3.0 HTHS, I hope.
 
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