Which oil is thicker? GC 0w-30, or M1 0w-40?

[LSVTEC 91 Civic]

I know I've heard of GC being almost a 40 weight oil , and I've also heard of 30w M1 oils shearing down to almost a 20 weight.. so I'm just trying to figure out which oil is thicker at operating temperature.

With that said, who is the winner?

 

[SSDude]

Initially, the M1 is thicker. Then, in a few thousands miles it will shear down to a medium weight 30wt. Then, around 10,000 miles it will thicken back up into a 40wt. In between 2,000-10,000 miles, I would say that GC is thicker.

 

[Bobert]

M1 0w-40 is thicker operating temp, but it tends to shear down sometimes to a thick 30wt. especially in turbo applications. GC starts as a thick 30wt but tends to stay in grade better. M1 0w-40 does pretty good though in normally aspirated engines and won't shear as badly.

 

[MattBrew]

what does shear down mean?

 

[haley10]

quote:

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Originally posted by LSVTEC 91 Civic:
I know I've heard of GC being almost a 40 weight oil , and I've also heard of 30w M1 oils shearing down to almost a 20 weight.. so I'm just trying to figure out which oil is thicker at operating temperature.

With that said, who is the winner?

---

SSDude and Bobert have good answers, but...as far as M1 30's shearing, I'd say no!!

Some engines can, but M1 10W-30 is extremely shear stable in general. It is one of the more shear stable oils I've seen of the shelf.

If you are shearing M1 10W-30 to a 20 wt. then ....other options needed to be explored.

Sorry for being

 

[y_p_w]

quote:

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Originally posted by MattBrew:
what does shear down mean?

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That it contains viscosity index improvers (VII), which tend to break into smaller pieces after use. It's believed that it's deliberately designed to do so such that the oil is slightly thinner after use, which helps with fuel economy. But at the tail end of the sequence test, oxidation thickens the oil enough that it still meets the "stay in grade" requirement of ACEA A3. Neat trick.

 

[John_E]

Does anyone have hard data regarding viscosity shearing of Mobil 1 0W-40? I have limited anecdotal evidence, in the sense that I get no oil consumption initially, then a little as the oil ages. By the way, I stick with a 3k mi /5K km OCI because it's an Audi 1.8T engine subjected to city driving.

 

[Audi Junkie]

Which is thicker? Depends on the temp you are talking about.

I don't have the plots for lower temps, but for example M1 is 14cSt at +100c and GC is 12cSt, but for the HT/HS at +150c, they are the same at 3.6. (Numbers are approx)

imo, it takes a better formulation to do that.

 

[LSVTEC 91 Civic]

Wow..

Well, the only reason I was considering M1 is because we don't have much more GC in this town..

Oh well, I don't know what I'll do yet.

 

[LSVTEC 91 Civic]

I'll run the M1 0w-40 then, I won't ever put 2000 miles on an oil change, because I hardly ever put miles on the car. It is my race car/toy

 

[YetAnother20V]

The 2 times I used M1 0W40 in my 1.8T, the engine ran hotter and noticeably louder.

This makes me want to believe that for F/I applications, a good, *heavier* 40 wt oil is definitely needed. I am not gonna do >5K OCIs in that motor, so the GC is staying out of that. No point in wasting money there.
Besides, I dont think it will survive the perils of a chipped, hard run 1.8T motor.

The GC is for my 2.0 litre iVTEC.

LSVTEC 91 CIVIC, since you are doing <2K OCIs, you might benefit from the more shear stable GC for your race applications.

 

[Volvohead]

You might think about M1 T&SUV 5w-40, which is about as shear stable as it gets.

Unless you must have the approvals that the 0w-40 carries (i.e. warranty compliance), then the T&SUV will do everything the 0w-40 can, and more.

 

[Audi Junkie]

Sorry, I see the original poster did mention a specific temp. Duh.