[s-cars] Re: Mobil 1 0W40

[J. Khang]

 --- CyberPoet <thecyberpoet at cyberpoet.net> wrote:
> Jonathan,
>
>    A multi-weight synthetic oil characterized as
> X-wY, where X is a
> numeric value (examples: 0/5/10/20/30) and Y is a
> higher numeric value
> (examples: 10/20/30/40/50) is stated to be:
> X is the actual base viscosity weight of the oil
> (compared to a
> 'traditional' dino oil) for pumping purposes, and Y
> is the
> characteristic viscosity standard of a similar
> quantity of
> 'traditional' oil at which the labeled oil as a test
> sample will
> perform before viscosity loss (due to thermal
> breakdown or sheer
> forces). Y is not to be confused as an actual weight
> of the oil at any
> temperature in a 0-wXX oil.

OK, Marc, I'll get back onto my design engineer's high
horse here and say that you need to look up the SAE
definitions again for multigrade oils. The LHS (xW)
refers to the viscosity when cold, measured at 40C.
The RHS refers to the viscosity when hot, measured at
100C. Rather than quote the actual viscosity which
would confuse the hell out of everyone, the SAE has
opted to indicate that the viscosity is equivalent to
the viscosity of a particular grade of mineral oil at
the same measurement temperature.

> synthetic) oil would. It does not mean that the oil
> actually alters
> it's weight as it heats, and only that zero weight

Oh yes it does, if by 'weight' you mean viscosity.
Viscosity is everything to a pump.

> is relevant for
> pumping purposes. If the auto manufacturer
> recommended oil-usage
> specification for a specific model calls for a 20
> weight oil in your
> ambient conditions, then a 20-w50 is suitable, but a
> 5-w30 is not.

Disagree. Asssuming linearity, the 5w30 oil will never
be less viscous than the 20 weight at any temperature.
It is, therefore, never 'thinner' than the 20 weight
oil.

Not unless you want to start discussing high shear
rate flows and molecular alignment.

> One other related note: Castrol at one point decided
> to blend a
> synthetic and non-synthetic oil and label it as a
> synthetic oil without
> reference to the fact that it was a blend. They had
> figured out how to
> match additives to traditional oils and get them to
> perform as if they
> were pure formulated synthetics (the conversion
> process cost them about
> 50% of the product cost of generating a pure
> synthetic). Naturally,
> they were promptly sued by a competing automotive
> oil firm (I think it
> was Mobil; the plaintiff  felt it was a deceptive
> practice). The result
> of the lawsuit with Castrol as the defendant, was an
> official court
> decision that mix-blends can still be claimed to be
> synthetic if they
> contain a synthetic portion, without regard to the
> actual percentages
> of synthetic vs. traditional dino oils. The
> consequence has been that a
> number of firms are now blending traditional and
> synthetic oils and
> labeling them as synthetic oils.

Incorrect. That lawsuit was about Type III vs. Type IV
base stocks and whether a Type III could be called a
synthetic as only Type IV base stocks were
traditionally called synthetics. Blending wasn't the
issue.

I am only contesting the claim that a 5w40, say, is
thinner than a 15w50. All your other anecdotal
evidence may or may not be true but I am not in a
position to judge. The SAE standard, however, is
clear.

Jonathan
'96 S6

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