Engine Oil Grades - what does it mean?

[sleepsus]

For those who wanted to know what those numbers on the engine oil bottles mean and how it relates to your car's engine, here is a good read :

HowStuffWorks "Choosing the Right Type of Motor Oil"

Viscosity, at its most basic, is a fluid's resistance to flow. Within the engine oil world, viscosity is notated with the common "XW-XX." The number preceding the "W" rates the oil's flow at 0 degrees Fahrenheit (-17.8 degrees Celsius). The "W" stands for winter, not weight as many people think. The lower the number here, the less it thickens in the cold. So 5W-30 viscosity engine oil thickens less in the cold than a 10W-30, but more than a 0W-30. An engine in a colder climate, where motor oil tends to thicken because of lower temperatures, would benefit from 0W or 5W viscosity. A car in Death Valley would need a higher number to keep the oil from thinning out too much.
The second number after the "W" indicates the oil's viscosity measured at 212 degrees Fahrenheit (100 degrees Celsius). This number represents the oil's resistance to thinning at high temperatures. For example, 10W-30 oil will thin out at higher temperatures faster than 10W-40 will.

[Bitulo]

In choosing which oil to use, there are two basic information that one should know: the viscosity grade which is indicated by the SAE number and the API grade. The SAE grade (Society of Automotive Engineers) shows how thick is the oil at operating temperature, i.e., 210 degrees F. The SAE 50 is thicker than SAE 40 and SAE 40 is thicker than SAE 30. In the Philippines where the temperature is relatively hot, recommended oil is SAE 40 and SAE 50. The right thickness is indicated in your car owner's manual. The SAE 50, SAE 40, SAE 30 are so-called single grade or monograde oils and SAE 10W-40, SAE 20W-50 are called multigrade oils. Under normal conditions, the multigrade oils are more expensive, but they provide better protection for your engine especially if you go to colder areas like Baguio once in a while. The rule of thumb is use whatever is the SAE grade in your car manual. Using thicker than recommended will unnecessarily burden your engine, but using lighter oil on the other hand may shorten your engine life.

The API grade indicates the quality level of the oil. Latest model cars are recommended to use API SM grade which is the highest level at this time. Older cars usually are recommended to use lower API grades like API SL, SF, SG, SE, SC (the lower the alphabetical designation the lower the quality level). Whatever model the car is, it can benefit by using the highest API grade available in the market. However, for those who want good protection for the engine at reasonable cost, the best bet is to stick to the recommendation of the vehicle manual. However, exceeding the API recommendation is a good practice for better engine protection but more costly.

[dvldoc]

If you every mix grades you might find this very handy.

Mixing viscosities

[hinDMaxsiado]

The TRUE viscosity of oil is NOT in the label of the package.... Those written in the label are just "indicative", not exactly the true oil weights nor viscosity.

True viscosity is measured kinematically and is given in centiStokes.... There are oil that are written as lightweight oils but are in fact a bit heavier when measured in their true dynamic viscosities at diferrent temperature levels.... There are even those that are written a bit heavier but are in fact not that heavy when you see their kinematic viscosities....

i purchase my oil based on its kinematic viscosities at different temperatures, amongst many other factors.

[locoroco777]

how will the common people know if whats the kinematic viscosity of the oil their buying? because last time I checked, none is written on the label, whats there is only the API rating, and winter temp and viscosity rate...

[indiej]

two 5w30 oils: one is 70 cSt at 40 deg C, the other 50 cSt same temp.

Is that at all significant especially at startup, when engine wear usually happens?
we have 30-35 deg C on good days, 22-28 deg C yuletide season. at lower temps both oils will have higher kinematic viscosity values.

[indiej]

how will the common people know if whats the kinematic viscosity of the oil their buying? because last time I checked, none is written on the label, whats there is only the API rating, and winter temp and viscosity rate...

you could search it in the net. e.g. below, i just googled that this minute


Castrol GTX
Method 5W-20 5W-30 10W-30 10W-40 20W-50
Viscosity * 100C, cSt ASTM D445 9.1 10.7 11.31 14.3 18.09
Viscosity * 210F, SUS ASTM D2161 56.1 61.7 63.9 75.2 90.4
Viscosity * 40C, cSt ASTM D445 51.77 64.31 75.1 108.3 159.1
Viscosity Index ASTM D2270 158 157 142 133 126
Low Temperature (C) Cranking
Viscosity, cP max. ASTM D5293 6,600 * -30 6,600 * -30 7,000 * -25 7,000 * -25 9,500 * -15
Low Temperature (C) Pumping
Viscosity, cP max. ASTM D4684 40,000 * -35 40,000 * -35 50,000 * -30 60,000 * -30 60,000 * -20
HT /HS Viscosity, cP min ASTM D4683 2.6 2.9 2.9 2.9 3.7
Pour Point, F (C) max ASTM D97 -44 (-42) -38 (-39) -22 (-30) -27 (-33) -27 (-33)
Flash Point, PMCC, C min ASTM D93 >200 >200 >200 >200 >200
Density * 15C, Relative ASTM D4052 0.862 0.862 0.878 0.887 0.884
Pounds per Gallon 7.18 7.180 7.314 7.387 7.364

* Due to continual product research and development, the information contained herein is based on products purchased in the U.S. subject to change without notification. Typical
properties may vary slightly.

[indiej]

after some reading around, i found that 5w30 are about 175 cSt at 20 deg celsius while heavier weight oils can go up to 600 cSt. a wonder how they pump that oil and what happens to those engines at cold crank. i put 1 liter in the fridge (labeled it 'gravy') not so concerned anymore. and there's the pour point.

as long as i follow the oil specs and change intervals, i'll have to trust the motor designers/engineers to have thought about cold cranking lubrication among other things. they are far and away the experts.

i also found that some oil may have no diesel api rating but their ilsac or acea rating covers usage for diesel engines

[arsen]

These are the corresponding test temperature range for the number before the W
0 = tested to remain fluid * -30 to -40 degree C
5 = tested to remain fluid * -25 to -35 degree C
10 = tested to remain fluid * -20 to -30 degree C
15 = tested to remain fluid * -15 to -25 degree C
20 = tested to remain fluid * -10 to -20 degree C
25 = tested to remain fluid * -5 to -15 degree C
We never experience those Winter temperatures in the Phils so we should not care about the numbers prior to W
-20 to -40 degree C is already extreme (in my field of work, it will trigger an automatic shut down of the machine)
Also at -40 there is no reason for the engine to start or continue running unless it is being used as genset or snow mobile in the polar region... heheh.

For the multi SAE grade XXW-YY, the XX is the base added with viscosity index improver (additives).
The base is the lubricant while the additives are added for the main purpose of improving the viscosity index and for additional function/selling points like cleaning capabilities and etc.
The lesser the number prior to the W the thinner is the base lubricant being used in the oil mixture. The corresponding test temperature range will give us an idea how thin is the base lubricant in order to remain fluid at extreme temperatures.

Oil is used in the engine for the main purpose of lubrication, cleaning should be secondary and being able to perform during winter is none of our concern or not applicable in the Phils. heheh.

What we should consider is the availability. Since manufacturers are also aiming for a universal market or a "one size fits" all product. It is expected that the most abundant oil or the oil grade in competition is in the mid-range 10W-30, 15W-30, 15W-40.

Also there are regulatory agency like API that sets the standard for the quality. So instead of going deeper to the mechanical and chemical properties, what we should be looking for is the API rating like:

CI-4 for high performance diesel engines with EGR (having EGR problem? might be due to your engine oil)
or
the current highest rating of CJ-4 which is recommended (or specially developed) to help protect both the "clean diesel engine" and to protect the diesel exhaust after treatment system like the diesel particulate filters (DPFs).

IMO SAE 15W-40 with API rating of CI-4 or CJ-4 is ideal for diesel engines in the Phils.
Of course subject for availability, price, reputation of the manufacturer and the dealer.

See the link for the list of oil manufacturer and brand names (as recommended by a car manufacturer)
click this link

Dapat pinagkakaabalahan naman paano malalaman ang genuine sa fake.