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#1826758 - 03/22/10 10:33 AM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: Nyquist]
Brian Barnhart Offline


Registered: 05/26/03
Posts: 573
Loc: Ohio
UOA wear numbers are low, which seems fairly typical for this engine. There is probably significant fuel dilution in this engine (even though itís not apparent in the fuel number). That would seem to explain why the shearing and flashpoint are not what one would expect to see in a synthetic after only 2.7K.

The OLM for this engine probably would have gone over 8K on this OCI before reaching 0%. That seems rather long given the shearing and flashpoint numbers in this UOA report.

Based on what I see here, a dino probably would have performed just as well in this engine under these conditions.

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#1826950 - 03/22/10 01:12 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: Brian Barnhart]
21Rouge Offline


Registered: 06/04/05
Posts: 1935
Loc: Vinegar Hill
Originally Posted By: Brian Barnhart
UOA wear numbers are low, which seems fairly typical for this engine.

Based on what I see here, a dino probably would have performed just as well in this engine under these conditions.


But might there be reasons to think that a synthetic oil performs better (than a dino) in the presence of fuel? i.e. better resists shearing or even with comparable shearing still protects the engine better?

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#1826987 - 03/22/10 01:39 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: 21Rouge]
Brian Barnhart Offline


Registered: 05/26/03
Posts: 573
Loc: Ohio
I didn't spend much time looking at other Ecotec results, but from what I've seen, the evidence doesn't seem to support the idea that synthetic (or at least this particular synthetic) performs better than a dino in this application. Both shearing and flashpoint have degraded significantly and rather quickly. Vis and FP for this oil are no better than this dino in another Ecotec with nearly twice the OCI. Plus, the M1 started out thicker and synthetics usually have greater initial flashpoints.

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#1827108 - 03/22/10 03:21 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: kender]
TomYoung Offline


Registered: 06/06/08
Posts: 478
Loc: New Jersey
Every 1,700 miles roughly? Sure hope you are using one of the high-end synthetic oils:)

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#1827116 - 03/22/10 03:30 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: ARCOgraphite]
TomYoung Offline


Registered: 06/06/08
Posts: 478
Loc: New Jersey
Originally Posted By: ARCOgraphite
Start up noise, hot running noise, rough running and tappet noise and car wouldnt rev over 4K rpm which is indicative of insufficent hot viscosity. The VVTi is very sensitive - Toyota 1nzfe ECU require a re-flash if you run 20w oils. As soon as I did the OC car ran perfect (after a couple days babying it during the add pack changeover).



Are you saying that the engine would not rev past 4k due to the oil degradation.... I don't think so.

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#1827294 - 03/22/10 06:07 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: TomYoung]
JAG Offline


Registered: 10/23/05
Posts: 4513
Loc: Fredericksburg, VA
3 comments below are in response to some other posters' comments.
1) Part of what makes this an "Advanced Fuel Economy" oil for an XW-30 oil is the initially low HTHS viscosity (2.99 cP) and the poor shear stability, making the used oil HTHS drop significantly further.

2) Viscosity loss from mechanical shearing happens very quickly and stabilizes as more and more of the polymeric viscosity index improved get broken, since they become harder to break the smaller they are. By 2700 miles, most of the mechanical shearing is complete.

3) Used motor oil flashpoint is dominated by the amount of fuel so the virgin oil's flashpoint doesn't factor in.

Wear looks fine. This engine appears to be a breeze on oil.

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#1841334 - 04/01/10 04:12 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: TomYoung]
sbergman27 Offline


Registered: 03/12/10
Posts: 371
Loc: Oklahoma
Quote:
Are you saying that the engine would not rev past 4k due to the oil degradation.... I don't think so.


What he's implying is that the oil had sheared to such a low viscosity that the vvt-i actuator couldn't function, leaving the valve timing in the fully retarded setting.

I don't believe that for a moment, of course. (And would love to see an independent reference to this supposed "known problem".) But that's what he's saying.

Toyota issued a TSB for his (an my) engine OK'ing use of 5w20 in them back in 2006, which didn't mention anything at all about vvt-i problems or an ECU reflash. So that should settle that.

-Steve


Edited by sbergman27 (04/01/10 04:16 PM)

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#1843173 - 04/02/10 11:58 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: addyguy]
chet2 Offline


Registered: 07/19/07
Posts: 1408
Loc: NH
so oil couldve gone 8k according to OLM even in nasty weather... i used to change my oil every 3-4k or so till i knew how long oil could really go...now i go at least 6k and that is conservative

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#1843174 - 04/02/10 11:59 PM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: chet2]
chet2 Offline


Registered: 07/19/07
Posts: 1408
Loc: NH
how was mpg on the 0-30?...i have a ecotec too

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#1844423 - 04/04/10 08:06 AM Re: Mobil 1 0w30 2008 Chevy Cobalt 2.2L Ecotec [Re: Nyquist]
fdcg27 Offline


Registered: 09/25/09
Posts: 8953
Loc: OH
Wear looks pretty good.
It would be interesting to see a UOA of a longer run with this oil, which would settle the question of whether you reached a point where shear stability had been reached, or whether shearing would continue in a linear fashion.
I put this oil in a friend's G5 2.2.
My logic was that the oil should be just fine down to 0% OLM and beyond, while delivering good cold-weather performance, and enough fuel economy improvement to cover its cost ($12.00 after MIR).
I also thought that the low HTHS was just fine for this engine, since it cannot impose the kind of loads and heat that would require a higher HTHS, and HTHS was apparently not something GM found necessary to account for in their OLM logic.
I currently have this oil in my '99 Accord as well.
Also used it as a winter fill the previous year.
I have a third jug for next winter, all of it cheap after MIR.
_________________________
12 Accord LX 22K HGMO 0W-20
09 Forester 64K PU 5W-30
02 Accord 127K G-Oil 5W-30
01 Focus ZX3 98K Synpower 10W-30
95 BMW 318iC 146K Defy 10W-40

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