What does 10 & 40 mean in 10W40?
Alnoor Mamdani
GUYNN, RICHARD CARL
10W40 indicates that the oil is a multi-viscosity type that has a range from 10W
to 40W grade. The viscosity (thickness) of the oil changes with temperature.
Sharen A. Rund
Its a multiviscosity oil that will run good in engines when the temperature
is <10 & >40, in other words, it's one of the most all-around oils to put
in your car (another is 10W30)
Christer Palm
What kind of engine has that temperature as while runing, the normal runing
temperature is aprox 185 F or 85 C
No it's the min and max viscosity (thicknes). The oil viscosity will not
be > 40 in a cool engine and not < 10 in an engine runing at normal
temperature aprox 185 F or 85 C for gas engines the thing is that you can't
start your engine in wintertime without this viscosity max limit.
--
"Destiny makes relatives, selection makes friends."
richard welty
>>Can anyone tell me what the numbers in oil
>>weights mean?
>Its a multiviscosity oil that will run good in engines when the temperature
>is <10 & >40, in other words, it's one of the most all-around oils to put
>in your car (another is 10W30)
er, this is the second wrong answer to this question to be posted;
where are the correct ones?
the numbers are indices into a pair of tables. one table is for
Apparent Viscosity at 0 degrees C; the other table is for Viscosity
100 degrees C.
numbers which are _suffixed_ by the letter W (e.g. 10W, 15W) are indices
into the Apparent Viscosity@0 degrees table. this characterizes the
oil's behaviour at freezing. a lower number indicates that the oil
flows better at that temperature; e.g. a 5W flows better than a 10W
that flows better than a 20W. here, flow is good because you want the
motor to lubricate quickly when cold. the owner's manual for your car
will indicate what the manufacturer considers appropriate for this
viscosity number.
numbers which are not suffixed by a W are indices into the 100 degree
C table; again, lower numbers will have `flow' better. however, when
warmed up, you may not want as much flow, because when hot, you may not
get adequate lubrication. again, there will be a recommended range
in the owner's manual for your vehicle.
the difference between straight-grade oils and multi-grade oils is this:
multi-grade oils contain ``viscosity enhancers''; these additives
allow the oil to be (relatively) thin at cold temperature while staying
(relatively) thick at hot temperatures; this is _not_ to claim that
these oils get thicker when hotter, but merely that they don't get
thin as fast as straight grade oils.
why did i distinguish between viscosity and apparent viscosity above?
simple: oil is `newtonian' over most of of the normal temperature range,
but below a certain temperature (freezing is generally below this temperature)
the relationship between temperature and viscosity is non-linear (i.e.,
the behaviour of the oil becomes non-newtonian.)
cheers,
richard
--
richard welty 518-393-7228
we...@cabot.balltown.cma.com
Andrew Evans
SAAB turbo has an "apparent viscosity" of 10 at 0 deg Celcius, and 30
at 100 deg Celcius. This doesn't quite make sense, because the oil
will be thicker at 0 deg C than at 100 deg C, viscosity enhancers or
no. It seems to me that the numbers would be the other way around.
Viscosity of 30 at 0 C, 10 at 100 C. Did I miss something?
David Doshay
A little problem with the units (none) of temperature, or possibly just too
quick an explaination.
Oils have their viscosity (a mearure of how much shear the oil will support,
or more simply how thick the oil is) measured in a unit called its 'weight',
or W. The bigger the number the thicker the oil. All motor oils get thinner
as they get hotter, so there is some standard temperature at which the single
weight is determined. A multi grade oil is formulated to act like a thin oil
when cold, so that you can pump it out to distant parts of the engine when
starting a cold engine in the winter, and like a thick oil when hot, so that
it does not thin out so much that it stops lubricating when you are climbing a
long hill on a hot summer day. In other words, they formulate the oil to
maintain an acceptable viscosity over a larger temperature range.
There is plenty of disagreement in the aviation
world about multi-weight oils: most people use a straight 50W. But there the
engines are not at all like modern auto engines. They are esentially a 1950
vintage VW type engine with a much larger displacement. All of the clearances
are much larger than any modern auto, because of different use cycle ( usually
just 3 power settings: full, 75%, and powered back for decent), so the cooling
situation is much different. The engines expand and contract LOTS more than an auto engine with a thermostat and water cooling. However, multi grades are
growing in popularity.
I use 10W 40 in any car that does not explicitly say not to in the manual.
10W 30 is probably just fine in any reasonably new engine (after breakin),
but of course it all depends a bit on how hot or cold your weather is.
I have tried both in my airplane. Right now I use 50W because the oil is
changed very often and it is lots cheaper.
David dos...@ursa.arc.nasa.com
richard welty
>In article <1992Feb3.2...@novell.com>, amam...@novell.com (Alnoor Mamdani) writes...
>>Can anyone tell me what the numbers in oil
>>weights mean?
>10W40 indicates that the oil is a multi-viscosity type that has a range from 10W
>to 40W grade. The viscosity (thickness) of the oil changes with temperature.
the thing is that 10W40 means 10W and 40 (not W); the W (winter) weights
are specified at 0 degrees C and the `not W' weights are specified at 100
degrees C
Thatch Harvey
the 10W (W stands for winter) means that at cold temperatures the oil
has the viscosity (thickness) of a straight 10 weight oil at the same
temperature. The 40 means that at operating temperature the oil has the same
viscosity as a straight 40 weight oil at operating temperature.
Having multiple viscosities allows you to get good oil circulation when
first starting and not have the oil too thin when the engine is hot.
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% (206) 335-2083 Merkur XR4Ti, Suzuki GS750EX, %
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Brian J. Queiser
>
> the 10W (W stands for winter) means that at cold temperatures the oil
>has the viscosity (thickness) of a straight 10 weight oil at the same
>temperature. The 40 means that at operating temperature the oil has the same
>viscosity as a straight 40 weight oil at operating temperature.
>Having multiple viscosities allows you to get good oil circulation when
>first starting and not have the oil too thin when the engine is hot.
>
I said this once last year. Prepare for the wrath of the net.
Regards,
Brian
---------------------------------------------------------------------
I am the engineer; I can choose K.
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que...@gn.ecn.purdue.edu
School of Aeronautics and Astronautics
Purdue University
West Lafayette, IN
richard welty
yes, you did. i also said that the numbers 10 and 30 were indices
into tables. admittedly, i neglected to make clear that two different
tables were used for the 0 degree viscosities and the 100 degree
viscosities; they are in fact different tables, meaning that the 10w
and the 30 numbers aren't directly comparable.
Jonathan R. Lusky
automotive lubricants for a living were of the opinion that 10W-40 required
too many viscocity enhancers to achieve its range of viscoscities and as a
result it broke down too rapidly. I use 10W-30 unless specifically specified
otherwise. Many new cars are spec'd for 5W-30 in most climates. I use
Mobil 1 15W-50 in my Rx-7 (79 Rx-7, dedicated CSP autocross car).
Jonathan R. Lusky
Paul Harvey
I use only SAE-30, (in CA)
Since it has no viscosity enhancers, it is always SAE-30!
You ever change your oil and notice the old oil was the thickness
of water? It was probably SAE10W-30 that broke down to its base of SAE-10!
Yet another reason to change your oil every 5K, although it's very good
practice if you use straight-weight oil also!
Lon Stowell
>
>I use only SAE-30, (in CA)
>Since it has no viscosity enhancers, it is always SAE-30!
>
>You ever change your oil and notice the old oil was the thickness
>of water? It was probably SAE10W-30 that broke down to its base of SAE-10!
Good thing you are in California. Have you ever tried to POUR
30 Weight oil at about 10 degrees F.....only to discover that it
is a mite thicker than Vaseline?
Tends to make it real difficult for your engine to produce enough
horsepower (when starting...low rpm) to turn itself over with
that nice thick oil. Often it doesn't....your engine will fire
and turn briefly, but as soon as the starter kicks out it
dies...usually due to simplistic use of the wrong oil for the
temperature.
Ernie Corley
AS THIN AS WATER????
I find it hard to believe that you could tell that much difference. After
all, when you pour new 10W/40 into the crankcase, isn't it by definition close to
a 10 weight??? Unless, of course, you like to heat your oil to 100 degrees C
before hand. I think there is very little "visible" difference in viscosity
between say a 10 and a 30 weight motor oil. I recently changed my gear lube
(75W/90) and it looked about as thick (or thin) as regular motor oil.
Paul Harvey
>I find it hard to believe that you could tell that much difference. After
>all, when you pour new 10W/40 into the crankcase, isn't it by definition close to
>a 10 weight??? Unless, of course, you like to heat your oil to 100 degrees C
>before hand. I think there is very little "visible" difference in viscosity
>between say a 10 and a 30 weight motor oil. I recently changed my gear lube
>(75W/90) and it looked about as thick (or thin) as regular motor oil.
I don't get it.
Are you saying you can't tell the difference between
SAE10 (sewing machine oil) or SAE30 (engine oil) or SAE90 (gear oil)?
Try pouring them at room temp sometime, I think you'll notice a diference!
Of course the multi-weight oils are a little different story, but I
think you will notice a difference between gear oil and engine oil if
you try pouring them!
All I was saying was that, from my experience, when you use SAE10W30
and you drain it after 5k miles from a hot engine as is ussual practice,
it has the consistency of SAE10 because the additives to make
it SAE30 at high temp have broken down. Any SAE10W30 eventually becomes
an SAE10W10 when the thickening additives break down. If you use SAE30,
it is always SAE30 assuming no water or gas is added and of course using
a straight oil has other problems as has been discused.
richard welty
>all, when you pour new 10W/40 into the crankcase, isn't it by definition
> close to
>a 10 weight???
well, not really; the curve _is_ linear over most of its length, so
if you figure that ambient is about 20 degrees C, you are up the scale a
little bit from 10W
> I think there is very little "visible" difference in viscosity
>between say a 10 and a 30 weight motor oil. I recently changed my gear lube
>(75W/90) and it looked about as thick (or thin) as regular motor oil.
bad example. gear lube viscosity indices go with a completely different
set of tables; a 75W90 gear oil may well have viscosity properties
similar to a 10W30 motor oil.
as for me, i can definitely see differences in how motor oil pours
depending on ambient temperature, and i can definitely see differences
in how 10W, 15W, and 20W motor oils pour.
as always, your mileage may vary.
cheers,