Originally Posted by BusyLittleShop
Then its possible Lucas 50 grade would test faster then the 20W and qualify as a 15W or 10W...
It's possible that it's a 0W too...but not likely.
Originally Posted by BusyLittleShop
API ranks the first number and the letter W from the slowest to the
fastest on its ability to lube your engine during critical start up because
the most wear happens during startup before pressure is establish...
No, that's incorrect...it occurs during warmup...you've pulled enough stuff apart to know that engines aren't "dry" when you start them.
Originally Posted by BusyLittleShop
Technically speaking the number and W is not a flow test to simulate
start up because oil don't flow much at minus degrees rather the W is
a API test where a cup of oil is stabilized to minus degrees and then
stirred by a precision motor / magnet and the amount of milli amps it
takes to move it in the oil are recorded and compared to the chart
attached...
The tools that are used to test viscosity are called "viscometers"...all the way from your "gravity flow" devices that you talk about to the "rotary" viscometers that you are trying to explain here.
W grades are measured for the MRV, which is the viscosity in a Mini Rotating Vscometer, where they have to achieve a maxmum limit, and not display a shear stres point...which ensures that ot will flow to the pickup.
And they do a CCS, cold cranking simulator, which tests the ability for an engine to turn over.
Originally Posted by BusyLittleShop
Quote Dan Watson who really knows that W measures in say a 10W test...
http://www.youtube.com/embed/E_iN_IJpSIU
"To test how oil will function in cold weather they don't flow the oil
because it would not flow through the orifice instead API takes a cup
and they fill it full of oil and lower it to the temperature required
they stabilize the temp to 0 degrees they set the cup on top of a
magnetic stirrer with a precision motor that turns the magnet. In the
oil is another magnet that magnet suppose to follow the outside magnet
the motor is connected to a precision milli amp meter which measures
amps in milli amps or 1,000 of an amp. the amount of current it takes
to turn the magnet in the cold oil is what is tested they set a range
on amperage if it will turn the magnet and draw 322 milli amps then
that qualifies as a 10w. to test for 5W they go down another 5
degrees and it stills has to achieves that amperage or lower. So what
are they really testing? the ability of the oil to lubricate a moving
part when its very cold will the oil actually allow the part to move
and not channel it can actually move in this cold oil and actually stay
a liquid if it actually does that they want to know how well it does
that the little precision motor will tell you how much energy it takes
to make the magnets turn that is a test of the resistance of moving
parts within the volume of oil. that is the trouble of cold oil can
you pump it? can you move it through gears can we get the oil to
move?"