GC- Cold Temp. Viscosity

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Oct 29, 2003
Ontario Canada
Guys. I've now switched to GC for my BMW.
I changed over last month before storing car.
My question is about cold temp. viscosity. I
read one post here that it is thicker than a
5w30 at most temps. So if it's -22 C (-10 F)
to 0 C (32 F), a 5w30 is better than a 0w30
because a 0w30's advantage is in extreme cold (Artic like tempertures.) How thick is it?
I always thought that all 0w30 oils had better
normal cold starting flow than 5w30 oils.
On a side note, I just saw the new 5w40
Bottles of Syntec which states on the back:
European Formula now Blended in The USA.

Will it be the same for the 0w30?
If so,
then everyone will be stocking up on the gold.
PS. I've built up a little stash of 22 bottles
of the green.
Those are great questions which probably can't be answered by the rank and file amateurs here.

I saw 427Z06 post (calculator based chart) but mistook it for actual oil specification. Does anyone know if it matches how oils perform at those temps?

A simple answer to your question is (which is simply my conclusion FWIW) - go with a authentic synthetic because it likely will reduce oxidation on the internals of a engine in storage due to it's cling behavior. 5w vs 0w is probably not as an important a factor.
My guess is that due to Euro-$ exchange rates, oil companies are moving as much "production" over here as they can. I seriously doubt this will result in lower quality product.
Steven88. The new 5w40 Syntec is now made or
blended in the States which means no more from
Belgium. I was told that the 0w30 grade will
also be made in the US. That means no more
GC. I know how people feel about Castrol
products being GRP 3 so I don't feel the US
stuff is the same. And if any of you think
a 0w30 cannot be a GRP 3, think again. I've
seen 0w30 oil from Petro Canada (one of the
biggest producers of GRP 3 oil) years ago,even before Castrol. I would feel better putting
oil from Germany or Belgium in my BMW.
Try to find a primarily Group 3 0W-30 oil that meets all of these: BMW LL-01, VW 502.00, 505.00, 503.01, GM LL-A-025 and LL-B-025, MB 229.1, 229.3, 229.5, ACEA A3,B3,B4. I've tried and could not. Meeting all of those specs requires the oil to be top notch.
Anyway, a little amount of Group 3 mixed in does not doom the oil to inferiority because an oil's performance is a function of both basetocks and the additives and Group 3 is not that far off PAO's in performance. An oil with lesser basestocks (some Group 3 mixed with PAO) but great additives can and has outperformed some 100% PAO oils. The thread recently posted about 5W-40 oil tests done by the Czechs shows this. Magnesium additive compounds come in many varieties and those used in today's oils are different than what they used to be, according to one of our forum experts: Molekule.

Castrol is a blender, not a raw material producer like Mobil or Chevron. Where Castrol does their blending tells us nothing about what materials they use.
Can anyone explain the "European Formula now Blended in The USA" statement he said earlier? I'm interested
Hmm I should probably dig up my notes and start a new thread in the general oil forum, but...

Last winter when I lived in central MA we had some of the lowest temps I've seen in a while. One morning when it was -5 degrees outside, I didn't dare shut the garage for fear of the doors freezing shut. In the morning the garage temp was 2 degrees inside! So I went over to my oil shelf and did some quick non-scientific tests, ie picked up a quart of each variety and shook it gently to see how the flow was. I recall that the GC, both gold and green, and PP 5W-20, were the best flow by a large margin. Not sure what else I had offhand, I recall I had M1 5W-20 and -30, PP 5W-30, plus Castrol, Napa, and Chevron dinos.

Hope that helps a bit...very un-scientific but nonetheless that is what I observed.
GC is a thick 30 that is probally more like 5w-40 at most temps, except the super-cold. If you want thinner at cold temps, get M1 0w-40.

GC is a thick 30 that is probally more like 5w-40 at most temps, except the super-cold. If you want thinner at cold temps, get M1 0w-40.

What's "cold temps"? Shall we say freezing point (0 deg. C)? At that temp, M1 0w-40 has a visc. of about 600 cSt, while the GC has a visc. of about 608 cSt, using the calculator above, so I'd say the difference is undetectable.
I used an online viscosity calculator to compare GC against Mobil 1 0w-40 a while back. I used the specs I found for Castrol Edge 0w-30.

Viscosity and Viscosity Index (VI) Calculation


Temp Castrol Mobil 1

F Syntec

0w-30 0w-40

Vi 167 187

100C 12.2 14.3

40C 72 80


-40 28357.7 19743.0

-30 14234.7 10603.0

-20 7591.9 5998.0

-10 4278.2 3558.0

0 2527.6 2199.0

10 1560.7 1412.0

20 1001.1 938.0

30 665.4 642.0

40 456.5 452.0

50 322 326.0

60 233.2 241.0

70 172.8 182.0

80 130.8 140.0

90 100.9 109.0

100 79.3 87.2

110 63.3 70.3

120 51.2 57.5

130 42 47.5

140 34.9 39.8

150 29.3 33.6

160 24.9 28.7

170 21.3 24.7

180 18.4 21.4

190 16.1 18.8

200 14.1 16.5

210 12.4 14.6

220 11.1 13.1

230 9.9 11.7

240 8.9 10.5

250 8 9.5


What about at -20 to -30 C and where did you get that information from? I've been looking lately...


TEMP ... M1 0w-40 ...... GC 0w-30


-20C ..... 2675 ............ 3046

-30C ..... 6765 ............ 8375

Use the calculator linked above. shanneba posted the two reference values (at 40C and at 100C) that you need to punch in in order to get the desired value at X degrees C.

It's an approximation though. From the figures above it shows that GC actually thickens up faster than M1 0w-40. Whether that's true in reality, I have no idea. I've never used either of these oils in temps lower than about -10C at which temp both flowed just fine.

From the figures above it shows that GC actually thickens up faster than M1 0w-40. Whether that's true in reality, I have no idea.

I was recently trying to decide between M1 0W-40 or GC 0W-30. I was concerned about the M1 being too thick during warmup, so I did a few quick experiments trying to determine the relative thickness of the oils at various temps. by timing how long it took for the oils to pour out through a hole in a small bottle (This actually remotely resembles a 'real' way to measure viscosity).

You should take the results with a big grain-o-salt, since I just used stuff laying around my basement... Hopefully, it should at least be good for relative thickness comparison.

But this is what I measured (Using M1 0W-40 numbers at 100C and 40C as a reference)


: 1F : 30F : 69F : 104F

Catrol Syntec Blend 5W-30: 74.1 Secs : 566 cSt : 150 cSt : 62 cSt

Castrol GC 0W-30 74.3 Secs : 586 cSt : 171 cSt : 73 cSt

M1 0W-40 96.0 Secs : 643 cSt : 183 cSt : 79 cSt

Castrol Syntec 5W-40 99.3 Secs : 773 cSt : ? : ?

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