Grade and weight correlation

[mjoekingz28]

I just dont comprehend.

My owner's manual recommends a 30 weight or a 30 grade oil......or is 30 weight THE grade?

Is weight referring to the kinematic viscosity at 100C?

In school
Grade A 91-100
Grade B 81-90
On and on


Oil in cST
Grade 30 (9.3 - 12.49). So, ten centistokes is the weight of a 30 grade oil?
Grade 40 (12.50 - 16.49)
An on and on


I just need reassuring sometimes. Thanks



Is weight even a legitimate term in regards to viscosity?

 

[Olas]

Weight is a term people sometimes use when they mean viscosity. The confusion isn't helped by the "W" designation of an oils cold flow characteristics.

For the purposes of answering your question, in ths case the weight IS the grade

Weight isn't really a legitimate term, although people know what it means, kinda like referring to your engine as a motor, it's an accepted colloquialism.

 

[mjoekingz28]

Ok, i appreciate it.

I got to thinking when the guy with a 1990 Miata showed a chart asking which oil to choose.

I thought ( straight weight ) and (monograde).

You watching Roland Garros?

Ya'lls will be here soon!

 

[Shannow]

mjoeking,
according to this
http://www.jcmotors.com/images/understanding_motor_oil_viscosity.pdf

Which contains some obvious errors in some areas, they state that the first version of J300 (1911), the "grades" were the time taken for a sample of oil to flow through a specific viscometer.

SAE10 was SAE20 was 15 to 24 seconds
SAE30 was 25 to 34 seconds
SAE40 was 35 to 44 seconds
SAE50 was greater or equal to 45 seconds.

I'm still trying to find a copy of J300 1911 to verify (lest I be accused of misleading), as I have only found this information once.

And it makes sense, when you look that SAE 20 had an inordinately long "specification" compared to the others (rectified in 2013 J300, when the 20 range was narrowed). Also, when Australian Penrite started making 70 and 80 "grade" engine oils, they claimed that they were extrapolated from the original concept.

 

[Shannow]

From the SAE
http://articles.sae.org/13555/

Quote:
One of the more mysterious aspects of motor oils is their grading system. In 1911 the Society of Automotive Engineers adopted the SAE J300 standard by which an oil is rated by weight, or viscosity. SAE J300 defined five grades, SAE 10 to 50, based an oil’s thickness when heated to water’s boiling point and how rapidly it flowed out of a specified size hole—faster flow got a lower rating; slower flow, a higher grade. Soon thereafter, the kinetic test was updated to use scientific units of viscosity rather than time, first in centipoise (cP), now in mPa.


Quote:
In 1952 the SAE added winter (“W”) grade designations (10W to 30W), which it defined by viscosities measured at 0° F (-18° C). At freezing temperatures an SAE 20 oil refined from black Gulf of Mexico crude was much thicker than an SAE 20 made from amber Pennsylvania crude. This difference came to be measured with a viscosity ratio metric called the viscosity index—the change in viscosity with temperature. The less a motor oil’s behavior changes from hot to cold, the higher its viscosity index, which is marked with a “W”. A 5W-30 motor oil performs like a SAE 5 motor oil would in the winter cold, but delivers SAE 30 viscosity at engine operating temperature.


So according to the SAE, the "W" stood for Winter, when introduced in 1952.

 

[Shannow]

Any of that helpful mjoekinz28 ?

 

[mjoekingz28]

Engne Lube 101

(....grading.......1911....SAEJ300.......oil is rated by weight, orviscosity.)




Yes thank you!