Dave M. wrote:
Wooops - think I got that confused with the lifter issue, which was
separate. (Sorry!) On second thought, I believe the lifter noise was
with the 0W-40 variety of M-1, and the noise would go away when
switching back to 15W-50 or 0W-40. Brian T wasn't impressed with the
0W-40 and someone else had less than stellar results too. I thought
Marshall had that with SynTec as well, but apparently my memory was on
the fritz and it was just a consumption problem (which IMO, is more
serious!) I think the 0W-40 is used as factory fill for fuel economy,
not for protetction... I wouldn't put it in my cars. YMMV, etc.
For reasons that escape me, the labeling of oil according to it's
viscosity at high and low temperatures seems to be much more a matter of
marketing than of science. The "40" of M-1 0W-40 is at the very low end
of the allowable range (12.5-16.3 cSt) of 40 weight oils right there
with the the high end of 30 weight oils (9.3-12.5 cSt). Nobody seems to
have grasped the idea that if we have 15W-xx oil or 5W-xx oil we COULD
also have xW-35 oil!
This is from the Advance Auto site:
http://www.advanceautoparts.com/english/youcan/html/ccr/ccr20010101ov.html
>>
Multigrade oils typically begin as base oils, such as 10W. Then
viscosity-index modifiers (polymers) are added in an effort to stabilize
the viscosity. This allows a 10W40 oil to flow like a 10W at cold
temperatures and a 40W at higher temperatures.
The multigrade oils' viscosity modifiers are long-chain molecules that
lessen the change of viscosity with temperature variance. In the past,
the polymer additives (used to thicken the oil) were sometimes
susceptible to viscosity loss. Permanent viscosity loss occurred when
high shear forces (such as the relationship between the main bearings
and the crankshaft) actually break the polymer molecules into
less-effective smaller pieces. On a similar note, temporary viscosity
loss also occurred when the polymer molecules aligned themselves in
order to create a path of least resistance.
Fortunately, today's additive packages have improved oil's
shear-resistance. However, oils with the same rating from different
manufacturers can exhibit different viscosity ratings in an operating
engine, depending on the shear stability of their viscosity-modifying
additives.
For technoids, weights are defined thusly (stokes and centistrokes are
measurements of viscosity):
"SAE 30 is SAE 30 no matter what the "W" prefix number is: 0W, 5W or
10W. This viscosity in centistokes (cSt) @ 100 degrees C is with the
minimum of 9.3 cSt and a maximum of 12.5 cSt.
"SAE 40 is SAE 40 no matter what the "W" prefix number is: 5W, 10W, 15W
or 20W. The viscosity @ 100 degrees C is within the minim of 12.5 cSt
and a maximum of 16.3 cSt.
"SAE 50 is SAE 50 no matter what the "W" prefix number is: 5W, 10W, 15W
or 25W. The viscosity @ 100 degrees C is within the minimum of 16.3 cSt
and a maximum of 21.9 cSt.
"SAE 60 is SAE 60 no matter what the "W" prefix number is: 10W, 15W or
25W. The viscosity @ 100 degrees C is within the minimum of 21.9 cSt and
a maximum of 26.1 cSt.
"There is no SAE 70 and no one is likely to make one with a "W" prefix
number although it is possible using a synthetic base oil. This
viscosity is identified as Grade 70. The viscosity @ 100 degrees C has a
minimum of 26.1 cSt and no maximum."
The difference between a multigrade and a singlegrade oil: The
singlegrade can't pass the low temperature viscosity test. If it did
meet one of the following "W" viscosities, it would be a multigrade.
Singlegrade oils will become obsolete for performance engines in the
future. We dropped SAE 30 and SAE 40 because SAE 10W40 does everything
30 or 40 can do—and some things the straight grades can't do—like
increasing horsepower. If an off-roader doesn't like 10W40, then use
20W50. It can do everything a 10W40 can do except pass the sub-zero
viscosity test at -20 degrees C.
Multigrade viscosities are run at six different sub-zero temperatures.
When a racing-oil designer puts a formula together, he has to know the
viscosity at 100 degrees C of every component in the additive
composition. He has to have a target viscosity objective for the
finished oil in each SAE grade. Once a formula is established, the
technician who supervises the blending has to duplicate this formula in
the correct proportions every time the product is blended. The viscosity
at 100 degrees C has a plus or minus written into the oil's
quality-control specification.
Multigrade or Multi-Vis?
One oil manufacturer claims that "some people in the industry use
multi-viscosity as if it means the same thing as multigrade. An oil
cannot be multi-viscosity, but it can be multigrade by meeting the
viscosity requirements for SAE 30, 40, 50 or 60 and one of the sub-zero
"W" viscosity requirements. At one time, some oil companies labeled oils
SAE 10W, 20W30—as if the oil could be 10W and 20W at the same time. This
is impossible because 10W is measured at -20 degrees C and 20W is
measured at -10 degrees C, which eliminates the multi-viscosity theory."
>>
There is NO reason why a 0W-40 oil shouldn't work fine in a modern
engine (the film strength and lubricity is MORE than sufficient by a
VERY wide margin), but it MIGHT not be entirely suitable for an engine
with less demanding tolerances or one that had been run on considerably
more viscous oil for an extended period and thus required a more viscous
oil to fill in the voids! I'm NOT disputing that lifter noise returned
to Brian or Wray's engines when they changed to 0W-40 and diminished or
vanished with the return to 15W-50 or 5W-40. I wonder what would have
happened if the 0W-40 had remained in there for 10-20kmi? I would
(perhaps naively) expect the engine to quiet down as the oil allowed the
surfaces to take on and retain a smoother and smoother polish (just like
breaking in the engine all over again).
I fall back on the axiom that for automotive use, that as long as your
oil meets the shear tolerance, film strength and lubricity requirements
and contains appropriate additives, you should use the "thinnest" oil
you can afford (thin oil WILL be consummed faster so you WILL use more
of it and it will cost more to run it) as the thinner the oil is at cold
startup, the sooner the oil begins to lubricate and minimize cold
startup wear (by far the leading cause of automotive engine wear). In
special cases (like racing), the VERY high temp characteristics also
come into play, but not in MOST passenger car applications.
Marshall
--
Marshall Booth (who doesn't respond to unsigned questions)
"der Dieseling Doktor" [EMAIL PROTECTED]
'87 300TD 181Kmi,'87 190D 2.5 199Kmi, '84 190D 2.2 227Kmi, '85 190D 2.0
159Kmi, '87 190D 2.5 turbo 234kmi
Diesel Technical Advisor MBCA, member GWSection
http://www.dhc.net/~pmhack/mercedes/mbooth1.htm
