Syntec 5w50

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Patman

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This is something that's been bugging me for a while now, but I wonder how Syntec's 5w50 can qualify as a 5w oil? If you compare Syntec 5w50 to other 5w oils, the viscosity at 40c is quite a lot different. Most 5w30 oils have a viscosity of 50-60cst at 40c, but Syntec 5w50 is 110! So how can it be so much thicker at 40C, but yet in the cold cranking tests it's still able to pass the 5w specs? Or is this oil a borderline 10w50 to begin with?

I know the 40c spec is only one part of the picture, and 40c is a slightly warm temperature, but I still think the huge difference in viscosity at this temp does mean something. I just question the ability of this oil, when the 5w spec is figured out at -30C but this oil's pour point isn't much better than that, at -39C (which is not very good at all for a synthetic 5w IMO)
 
Patman, you keep bringing this up...and I thought we cleared up that the 5W is a cold cranking number. 40C is pretty hot...remember, it's not 40F. The 50 on the other hand is achieved at 100F and is 17.5. Therefore, at about 40F, it will be about 110.

In other words, the 5W is achieved due to it's Cold Cranking viscosity at -30C which is <6600...what happens after that is a dramatically diminished thinning relative to other 5W-x.
 
Not only that, but from what I've learned here, isn't that one heck of a spread for VI's?????
 
Can anyone say what the qualitative difference would be between the Castrol Syntec 5-50 with a Viscosity Index of 175 and Quaker State's Synthetic 5-50 with a Viscosity Index of 193. What does this number mean and how does it differentiate these 2 oils?
 
quote:

Originally posted by Dr. T:
Patman, you keep bringing this up...and I thought we cleared up that the 5W is a cold cranking number. 40C is pretty hot...remember, it's not 40F. The 50 on the other hand is achieved at 100F and is 17.5. Therefore, at about 40F, it will be about 110.

In other words, the 5W is achieved due to it's Cold Cranking viscosity at -30C which is strong>

I realize that, but my point is, if those two oils are so far apart in viscosity at 40c, how can they then be roughly the same at -30C, when the Syntec 5w50 isn't exactly using some super exotic base oil or anything.
 
quote:

Originally posted by Dr. T:
... the 5W is a cold cranking number. 40C is pretty hot...remember, it's not 40F. The 50 on the other hand is achieved at 100F and is 17.5. Therefore, at about 40F, it will be about 110.

In other words, the 5W is achieved due to it's Cold Cranking viscosity at -30C which is strong>

Nothing to add here except a typo correction:
"The 50 on the other hand is achieved at 100F ..." should read,
"The 50 on the other hand is achieved at 100°C ..." (This is the same as 212°F.)
and, "Therefore, at about 40F, it will be about 110." should read,
"Therefore, at about 40°C, it will be about 110°F." (Actually, I think 40°C is closer to 104°F.)

Just so everyone knows (& I'm sure most everyone does), Centigrade is based on water's reaction to temperature at sea level (since it reacts differently at altitude). 0°C is the temp at which water freezes, & 100°C is the temp at which water boils.

Just trying to help out. I know I get confused enough as it is.

cheers.gif
 
Polymeric thickeners affect the viscosity of the oil at ALL temps, however they profoundly affect it at temps higher than room temp. The VI is defined as the change in viscosity between 40C/104F and 100C/212F. The higher the VI, the less the viscosity of the oil changes. One thing to note this that the relationship between viscosity and temp is non-linear. So you can't just plot the viscosities @ 40C/100C and draw a straight line through them to determine the viscosity at much lower temperatures....

Most of the effect of polymeric thickeners seems to occur between 40C and 100C. So if you see an oil with a VI of > 175, you can be sure it has some VI modifier in the formulation. I'd estimate the best you are going to do from the basestock blend alone is a VI in the 160-175 range. This is based on the observed behavior of multigrade oils in actual use and how much they tend to shear ....I haven't seen any oils - regardless of price - with VI's > 175 that are completely shear stable. Some cheap oils with VI's
It is the VI rather than the SAE grade that is the best indication of shear stability. Look at the VI's of the 5w-20/10w-30/15w-40/20w-50 grades - those are about the practical VI limit, for completely shear stable formulations, in reasonably priced oils.
 
Which would lead to a conclusion that Syntec 5w50 is loaded with VI Improvers to produce such high VI of 193 and to achieve the 5w to 50 spread. I really don't see a need for this multigrade for most cars on the road today.
dunno.gif
 
This was part of Castrol's first entry into synthetics. I doubt you would get their recommendation to run it in anything of modern design. They make it available, but.....

Probably not worth loosing any sleep over. It's pretty much obsolete.
 
quote:

Originally posted by Eiron:
Patman,

I don't know if this helps, but Mobil's 5W-40 is 102 cSt at 40°C.


I've always felt that was kinda high too though, this was another reason I never felt compelled to run Delvac 1 in my car in the winter.
 
I will have to rerun the 5W50 test. I cantaminated the oil. My curiosity got the better of my. My simple unscientivic results are in the MMO post someone else started!

I highly recomend looking at my results as a what not to add to your oil type of thing! This car is kind of a test mule for things like this!
 
quote:

Originally posted by Audi Junkie:
Is your query something that could be cleared up by a VOA? If so, I'll pop for it.
wink.gif


Not really, this is something a VOA can't really help us figure out. Although if you'd like to do one, that would be cool!
smile.gif
 
quote:

Originally posted by Patman:
This is something that's been bugging me for a while now, but I wonder how Syntec's 5w50 can qualify as a 5w oil? If you compare Syntec 5w50 to other 5w oils, the viscosity at 40c is quite a lot different. Most 5w30 oils have a viscosity of 50-60cst at 40c, but Syntec 5w50 is 110! So how can it be so much thicker at 40C, but yet in the cold cranking tests it's still able to pass the 5w specs? Or is this oil a borderline 10w50 to begin with?

I know the 40c spec is only one part of the picture, and 40c is a slightly warm temperature, but I still think the huge difference in viscosity at this temp does mean something. I just question the ability of this oil, when the 5w spec is figured out at -30C but this oil's pour point isn't much better than that, at -39C (which is not very good at all for a synthetic 5w IMO)


I think you make some excellent points. I've said this many times on the other topic "Best ..." that the dominant effect on lifetime engine wear is startup cranking. And you reduce startup cranking wear by running a thinner motor oil. Since thinner means bad at high temperatures, we'd better make that a synthetic. You are EXACTLY right in that Castrol 5w-50 is a bad choice for lifetime engine wear because it it too thick when starting-cranking. Therefore, the Imported-from-Germany Castrol synthetic 0w-30 (says Made in Germany on the back) is probably about the best for getting to your bearings the fastest at startup.

In the other topic ("Best...") I've asked everyone to chant "Most engine wear occurs at startup" just so we will remember that and avoid all 5w-50, 10w-30, 10w-40, etc. weights, unless racing a (see other topic "Best..." for more on special racing requirements).
 
I was checking super tech, at walmart in ottawa,
they advertise the synthetic 5w-30 has a pour point of -45c....

im not sure if this helps ???

just something to compare to
nik
 
Duh
pat.gif
yes I meant celcius.

Otherwise, here on the board I see it recommended for Japanese cars in Australia...seems like the members talk about M-1 5-50 used a lot.
 
check out the diferences between Mobil 1 OW/5W/10W at 40ºC?

cSt @ 40ºC/ 100ºC
OW-20 43/ 8.4
0W-30 56/ 10.3
0W-40 80/ 14.3
5W-30 56/ 10
10W-30 62/ 10
 
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