Does Dexos1 Gen 5W-30 stay in grade, or .....

[ammolab]

Mobil 1 Full Synthetic 0W-40 is Dexos “R” according to the Mobil site. It’s a thin 40 and if you read posts here long enough it’s the answer to almost everything.

I run it in my LS3 Chevy V8

 

[kschachn]

GM wengineers likely took into account the shearing of the oil weight they recommend for their vehicles. Just like they came up with their dexos requirements.

What would give you that impression?

 

[Plumb Bob]

I plan to keep the truck for a maximum of seven years or 62,000 miles.

Perfect plan, I mean it. Do the dealer OC and worry not about HTHS.

 

[DocTone]

GM recommends 5W-30 dexos1 Gen3 for my new Sierra HD 6.6 gas engine. I won't risk voiding my warranty, but I'm curious to know if the 5W-30 dexos1 Gen 3 maintains its grade or drops to a 5W-20 prematurely.

No it does not. I have a March built GMC Sierra 2500 and did the oil change after a break in of 674 miles. I wanted the Dexos out as it is not ideal oil. I'm using Castrol Edge Euro 0w40 SP and the remainder of my SN 5qts to 3qts. VOA blend of 1400ppm Cal. Edge 0w40 is same as Mobil 1 Full Synthetic 0w40 that has been fast tracked to Dexos R status. Same approvals. Dexos 1 Gen 3 is piss water. https://www.gmdexos.com/brands/dexosr/index.html Mobil 1 Full Synthetic 0w40 is being used in the lesser 6.2L L87 LT engine look that up. If you want a lower viscosity that beats Dexos and LSPI in DI engines Castrol Edge Euro 5w30 K or Mobil 1 ESP 5w30 these both have better European approvals that are way ahead of API

 

[DocTone]

For what it's worth this is my used oil analysis from BlackStone on the first run of Castrol Edge Euro 0w40. I mixed 5qts of API SP with 3qts ff API SN to use up my remaining stash of SN and not go over 1500 ppm Calcium. Looks to be a close Calcium amount in add pack compared to posted VOA of Mobil 1 Full Synthetic 0w40 SP. This sheared down to 30w which is were the 6.6L L8T requires. I feel this oil will serve as well as a Dexos R in this application as would Mobil 1 Full Synthetic 0w40

 

[kschachn]

For what it's worth this is my used oil analysis from BlackStone on the first run of Castrol Edge Euro 0w40. I mixed 5qts of API SP with 3qts ff API SN to use up my remaining stash of SN and not go over 1500 ppm Calcium. Looks to be a close Calcium amount in add pack compared to posted VOA of Mobil 1 Full Synthetic 0w40 SP. This sheared down to 30w which is were the 6.6L L8T requires. I feel this oil will serve as well as a Dexos R in this application as would Mobil 1 Full Synthetic 0w40

With a Blackstone analysis you have no idea whether there was shear in the VII or there was fuel dilution. They are useless for that determination.

 

[DocTone]

Fuel dilution was tested and not a issue. So I know the VII gave up. But I'm ok with it ending up at 11 cst after 5K miles. I'm not looking for long drain with a GDI engine. If I can figure out my problem attaching pdf's I'm put it up.

 

[kschachn]

Fuel dilution was tested and not an issue. So I know the VII gave up. But I'm ok with it ending up at 11 cst after 5K miles. I'm not looking for long drain with a GDI engine. If I can figure out my problem attaching pdf's I'm put it up.

Tested by whom and by what ASTM method?

If it’s really mechanical shear of the VM then I’d be looking at a no-VII oil or one with a more stable form. Mobil 1 0W-40 holds up well in my old 1MZ-FE with its gear driven camshafts.

 

[DocTone]

What does that oil end up as and what is the OCI?

 

[kschachn]

What does that oil end up as and what is the OCI?

My OCI varies over the past many years, but about 5000-7000 miles. It is within grade if that's what you're asking. There is fuel in the winter, or at least there used to be when we drove the thing a lot. Now it's just a transporter to the landfill and to take the dog to the dog park.

I've used several different 0W-40 brands but generally always something with Mercedes-Benz 229.5 approval or equivalent. I did get in on the super cheap Amazon 0W-40 clearance but I didn't check the oil on any of that.