5W-20 vs. 5W-30 vs 10W-30

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5W-20 and 5W-30 both pour the same when putting them into the engine and when the engine is first started which is 5W. As the engine reaches normal operating temperature, the 5W-20 thins into a 20 weight oil and the 5W-30 thins into a 30 weight oil. Both of these weigh less than 5W weight oil. So I am confused about the benefit of 5W-20 as opposed to 5W-30.

Also, in regards to 10W-30, the oil pours out as a 10W weight oil which is thicker and heavier than a 5W weight oil. When normal engine operating temperature is reached, both 5W-30 and 10W-30 have thinned into 30 weight oil which is lighter than 5W and 10W oil.

It just seems to me that 5W-30 is the best weight to use for most cars unless something like 10W-40 or 20W-50 is recommended.
 
Also, most engine wear occurs at start up so I still can't see the benefit in regards to 5W-20 and 5W-30 in that regard since they both weigh the same at that point but it is quite easy to see with 10W-30 since it is thicker.
 
Wrong.
5W20s have a slightly lower viscosity at room temp than 5W30s have, and usually a slightly lower minimum pumpting temp.
 
Buford, I think the answers to these questions will become self evident if you become acquainted with the SAE J300 Viscsoity Chart.

5W is a minimum 3.8 cSt @ 100C

10W is a minimum 4.1 cSt @ 100C

A SAE 30 viscosity grade oil is 9.3 to 12.5 cSt @ 100C.

quote:

both 5W-30 and 10W-30 have thinned into 30 weight oil which is lighter than 5W and 10W oil.

Based on the SAE J300 chart, this statement is off the mark.
 
The first number has more to with the temperature at which the oil goes solid. The second number is a much better indicator of the viscosity of the liquid oil at all temperatures, and is matched to the engine requirements.
 
That charts is a little confusing to me. I wonder why they didn't use the same temperature for the measurements for cranking and pumping?

But still the oil thins out has it gets warmer according to that chart...

5W = 3.8 Low-Shear-Rate Kinematic Viscosity(5)(mm2/s) at 100°C Min

30 = 2.9 High-Shear-Rate Viscosity(6) (mPa-s) at 150°C Min
 
quote:

Originally posted by TomJones76:
Wrong.
5W20s have a slightly lower viscosity at room temp than 5W30s have, and usually a slightly lower minimum pumpting temp.


That is true, but they both weight the same at 0° C right?
 
That article is an oversimplification. There are 0w30's that are thicker than 5w30's through much of the oils usefull temperatures. 5w20's are normally thinner than 5w30's at all temperatures.
All 5w or 10w indicates is the cold crank viscosity. That is all.
 
OK so therefore at cold crank, 5W-20 and 5W-30 weigh the same since they are both 5 winter weight?

But as the engine approaches normal operating temperature, the 5W-20 is obviously thinner than 5W-30.
 
Buford, what are you missing here??? Go look at product data sheets. Most, if not all 5w-20s have a lower CCS viscosity than their 5w-30 counterpart. Pennzoil for example: 5w-30 cranks 5800 Cp, 5w-20 5200 Cp. 5w-20 pumps 15,700 Cp and 5w-30 pumps 25,100 Cp.

Now, I'll use Pennzoil 5w-20 and 5w-30 to show that at any temperature, the 5w-20 is thinner. At -30C (where the 5w cranking test is measured at), the kinematic viscosity of 5w-20 is 6818 Cst. The 5w-30 on the other hand is 9315 Cst, about 37% thicker in measured viscosity. At any temp above that, the 5w-20 is still going to be much thinner. Lets go with 50 degrees F. Pennzoil 5w-30 is 296 Cst, where as the 5w-20 is 211 Cst.

[ May 14, 2006, 07:51 PM: Message edited by: Drew99GT ]
 
TYPICAL PHYSICAL AND CHEMICAL PROPERTIES
PENNZOIL® MULTIGRADE MOTOR OIL

Viscosity, cP (°C) ASTM D-5293 5w-20 = 5,200 (-30) 5w-30 5,800 (-30) 10w-30 5,900 (-25) 10w-40 6,090 (-25) 20w-50 6,890 (-15)

Now I don't know how significant the difference between 5200 and 5800 cP is ..but I reason that it's not all that much.

Now when you go to the warmer tested temps

40°C,cSt D-445 47.4 .63.9 70.1 ...94.3...155.3 @

100°C,cSt ASTMD 8.20 10.5 10.4 13.6... 17.5

You will see that the differnce in viscosity is approx 7-8 times as much at 40C as it is at 100C (2.3 vs. 16.5 for 5w-30 vs 5w-20)
 
The pre W number and post W number in a multi-viscosity oil represent a range. 5w means the oil can't crank more than 6600 Cp at -30C and pump more than 60,000 Cp at -35C. The other number, "30" for example, means the oil has to be between 9.3 and 12.5 Cst I believe. So even though 5w-20 and 5w-30 are both 5w, the 5w-20 is going to be much thinner at all temps, even super cold temps.
 
Buford, I THINK what is throwing you off is the idea of comparing how much an oil weighs. Viscosity has no relationship to how much an oil weighs. Viscosity is referring to how thick or thin an oil is...and it changes with temperature.

In a perfect world, a 5w-20 is the same viscosity as a 5w-30 when they are cold. But, when these two oils are warmed up to engine operating temperatures, the 5w-20 will be less viscous (or, to say it another way, it will be thinner) than the 5w-30.

Another point to keep in mind, the "w" after the first number means "winter", not "weight".

One last point, and this point is why the perfect world I mentioned above isn't necessarily so perfect: the viscosities of these oils are expressed in a range, i.e., there are oils rated a 20 weight that are on the thinner end of the 20 weight viscosity range, and some are so thick they are almost, but not quite, a 30 weight viscosity. You COULD have a 5w-20 that acts almost exactly like another oil that is rated as a 5w-30.

Then, to make it even more weird, Castrol makes a Green synthetic 0w-30 that is thicker along the entire temperature scale, except at something like minus 35 degrees, than almost any other 5w-30 weight! And, this 0w-30 can actually thicken so much during use it crosses over the imaginary line dividing the 30's from the 40's to become a 40 weight viscosity!

Clear as mud? GOOD!
 
I'm not sure the German "elfin" oil becomes a hot 40 viscosity grade ("weight") at operating temperature, but it's definitely a high-30. Funny how the European automakers are not buying into the 5W-20 mythos - even for the cars they sell over here. Oh, by the way, German Castrol 0W-30 is no longer blending green motor oil that carries an odor reminiscent of Gummy Bear candy. It's gone to stinky amber (or "gold" as its more poetic afficionados are prone to gush - still stinks though). There may still be unsold stock of the green-tinged oil legend that was eventually awarded its own BITOG discussion group.
 
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_5W-20.asp
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_5W-30.asp

Just looking at the numbers there, the performance appears to be pretty close between 5W-20 and 5W-30. Strangely 5W-30 pours at a lower temperature while being a bit thicker than 5W-20.

My car, a 1998 Ford Mustang GT, has the 4.6L engine that is qualified to run 5W-20 according to Ford. But would I want to? I don't know. It would seem to me the engine would make more noises and oil would start burning.
 
The 5w30 may have more PPD's tthan the 5w20. Do to the operating temp viscosity the base oil for the 5w30 is obviously higher in viscosity. Pour point is not as good a spec as cold crank. Keep doing your research. Here is a bit of a lateral comparison. Sorry for the sloppy format

TropArtic™ Synthetic Blend Motor Oil
Typical Properties
SAE GRADE 5W-20 5W-30 10W-30
Density,g/cm3 @ 15.6ºC (60ºF) 0.852 0.854 0.862
Color, ASTM D1500 3.5 3.0 3.0
FPºC(ºF) 224 (435) 221 (430) 224 (435)
Pour Point, ºC (ºF) -31 (-24) -31 (-24) -31 (-24)
Viscosity,
cSt @ 40ºC 48.8 64.0 66.0
cSt @ 100ºC 8.6 10.9 10.9
SUS @ 100ºF 248 325 336
SUS @ 210ºF 55.1 63.4 63.4
Viscosity Index 164 163 157
Cold Cranking Viscosity, cP 3,700 5,300 3,500
@ ºC
-30 -30 -25
HTHS 2.6 3.1 3.1
Sulfated Ash, ASTM D874, wt % 0.97 0.97 0.97
Total Base Number (TBN), ASTM D2896 7.8 7.8 7.8
Phosphorus, wt % 0.078 0.078 0.078
 
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