dexos oil

[Jworks]

2011 Sierra, 4x4, 5.3.  I know dexos is recommended for this model engine.  Dealer has done all my past oil changes except the last one, which I did myself with Mobil 1 High Mileage and Fram upper end synthetic filter **.  That was 4k miles ago, computer is showing 36% left, but regardless I will be changing oil anyway next week.  When I used Mobil 1 High Mileage I didn't think about it that I should be using a dexos oil (whatever that means).  Stupid of me, I know.  But it seems no harm done.  I'll probably let the dealer do the upcoming oil change and use their dexos synthetic again BUT with a better than standard AC Delco oil filter [UPF-48R].  Question is :  How is dexos different and why does GM recommend it for this (and newer) models?  I don't "think" I'll have any issues by going back to the dealer dexos synthetic and higher end filter.

 

** [Why I changed oil myself]  I previously had an oil pressure issue months ago.  Dropped to 21 psi even at hwy speed.  Engline light eventually came on to check oil sensor.  Engine never shut down.  I had the sensor replaced -- mechanic said the screen underneath it still looked very clean so he did not replace it.  So after the sensor change oil psi was up to 30 at hwy speed, still 22 idling.  He said though that was still well above GM minimum required specs.  Unsure about all this, I changed oil and filter as recommended by people on this site - and this time l did it myself.  The oil psi at hwy speed psi got to 40, sometimes goes to 38, but mostly 40.  Idling 30 psi with occasional 22 (but varies up and down, mostly 30).  I was told that that often those standard filters (even AC Delco) go bad and that causes the oil psi issue, so I should insist on the UPF-48R in the future.  Sure enough, after changing oil myself it was much better. 

[Grumpy Bear]

20 hours ago, Jworks said:

Question is :  How is dexos different and why does GM recommend it for this (and newer) models?

 

DEXOS is a GM license which says the oil passed a stricter standard than the API standard for the classification GM is calling for.

 

Example. GM DEXOS1 Gen2 standard for the API SN/SN+ classification for NOACK is about 13% while the API SN+ standard is 15% maximum. Cleanliness is also a tighter VG sequence test requirement of the DEXOS license because GM designs require it in hopes of limiting warranty claims. AFM/DFM systems and low tension rings require/like clean oil. Blenders pay GM a fee for this license. . 

 

Now having said that most major brand oils meet the specification for DEXOS. Many boutique oils do as well and yet not all choose to participate in the "shakedown". 

 

That is...there are oils that far exceed GM DEXOS standards that are not licensed by a wide margin and yet do not carry the seal of approval from GM. There are also oils out there that do carry the license that JUST meet the standard. 

 

Some of the over achievers are: Red Line HP. AMSOIL SS. RLI. Biosynthetic. EVOLVE. Schaeffers, to name a few.   

 

That should handle the how and why. 

 

BTW Exxon/Mobil makes GM's DEXOS licensed oils.

That does not mean however the AC-Delco oil is equal to Mobil 1 AP.  

 

Maybe James or @newdude will show up for the oil pressure questions. They know those years oil system layouts better than I.

Edited September 11, 2022 by Grumpy Bear

[Jworks]

Thanks Grumpy Bear.  Good explanation. 

[diyer2]

I would think Amsoil OE would meet Dexos requirements. 

[Grumpy Bear]

41 minutes ago, diyer2 said:

I would think Amsoil OE would meet Dexos requirements. 

 

Absolutely true. In fact one of the few oils to beat the ILSAC GF6A/API SP LSPI standards without reformulation. 

[pokismoki]

what was the engine temp, oil viscosity and engine loading at when the gauge read 20psi?

 

i know the computer controls the variable oil pump, but super thin worn out oil might also cause  a low reading.  then there is the two different oil filters GM offers that fit our trucks, one is low pressure , and the other is a higher  pressure bypass. you need the correct filter to jive with this computer controled oil system

Edited September 11, 2022 by pokismoki

[Black02Silverado]

Just curious as to how many miles are on your truck and why you used a high mileage oil?

[Jworks]

21 hours ago, pokismoki said:

what was the engine temp, oil viscosity and engine loading at when the gauge read 20psi?

 

i know the computer controls the variable oil pump, but super thin worn out oil might also cause  a low reading.  then there is the two different oil filters GM offers that fit our trucks, one is low pressure , and the other is a higher  pressure bypass. you need the correct filter to jive with this computer controled oil system

  Pokismoki, the motor temp when that happened was normal (210 degrees), its never overheated. 

The oil viscosity was 5w-30 

The engine was at normal highway speed pulling a boat (18 ft boat), about 2000 lbs on the boat & trailer.  Running 60-70 mph.  RPMs 1600-2000.

Also, I looked at the dealer's oil change ticket and it says the oil filter was PF48.  I never heard of a computer controlled oil system.  Thats news to me.

[Jworks]

12 hours ago, Black02Silverado said:

Just curious as to how many miles are on your truck and why you used a high mileage oil?

Black02Silverad, it had 141k miles at the time I did the oil change myself.  Currently it has 146k.

I had not done it myself in several years and opted to let the dealer do it.  This was my first truck to own specified to synthetic oil; I'd always used Castrol conventional oil in past trucks.  Because I'm 75 I ust decided to let the dealer do it.  But when this 21 psi issue happened I just decided to risk the cost of an oil change even though it was not time.  I did so based on recommendations by several people on here.  Since I'd never used oil myself using synthetic I chose to put in Mobil 1. I went with the High Mileage oil because the label on the oil can said "over 75,000".  Thats the only reason I went with that oil.  It was not using any oil that I know of.

 

 

Edited September 12, 2022 by Jworks

[Grumpy Bear]

https://www.motor.com/magazine-summary/trouble-shooter-jan-2017-low-oil-pressure-vortec/

 

That may be useful.

[diyer2]

How often have you changed the oil or your average mileage when changed?

[redvett]

DEXOS is a synthetic blend oil and you can use any full synthetic oil like Mobil 1 or similar oil.  My GM dealer researched this when i got my wife a 2011 Buick Enclave and brought it in for free first oil change.

[Jworks]

15 minutes ago, redvett said:

DEXOS is a synthetic blend oil and you can use any full synthetic oil like Mobil 1 or similar oil.  My GM dealer researched this when i got my wife a 2011 Buick Enclave and brought it in for free first oil change.

Thanks redvett.  You reminded me of something I had forgotten.  When I first got this truck I asked the service manager about Mobil 1.  He said he could put it in there, it'd just cost a little more than the dealer-provided GM dexos.  I had forgotten that.  Getting old I guess. 

1 hour ago, diyer2 said:

How often have you changed the oil or your average mileage when changed?

 

1 hour ago, diyer2 said:

How often have you changed the oil or your average mileage when changed?

diyer2, I go by what the computer shows.  When it gets to 20-30% remaining I go ahead and change it.  Thats around 5k miles.

[swathdiver]

Dexos1 Gen2 is fully synthetic oil.

 

It is normal for the oil pressure to drop during an oil change interval.  Some filters are also more restrictive and drop oil pressure.

 

I quit running Mobil One years ago as my motor would rattle on start up.  Switched to ACDelco oil and no more rattles.  M1 EP filter dropped my oil pressure 2-3 psi.  K&N filter with 1" nut on the end shows no loss of oil pressure.

[Jworks]

On 9/10/2022 at 11:43 PM, Grumpy Bear said:

 

DEXOS is a GM license which says the oil passed a stricter standard than the API standard for the classification GM is calling for.

 

Example. GM DEXOS1 Gen2 standard for the API SN/SN+ classification for NOACK is about 13% while the API SN+ standard is 15% maximum. Cleanliness is also a tighter VG sequence test requirement of the DEXOS license because GM designs require it in hopes of limiting warranty claims. AFM/DFM systems and low tension rings require/like clean oil. Blenders pay GM a fee for this license. . 

 

Now having said that most major brand oils meet the specification for DEXOS. Many boutique oils do as well and yet not all choose to participate in the "shakedown". 

 

That is...there are oils that far exceed GM DEXOS standards that are not licensed by a wide margin and yet do not carry the seal of approval from GM. There are also oils out there that do carry the license that JUST meet the standard. 

 

Some of the over achievers are: Red Line HP. AMSOIL SS. RLI. Biosynthetic. EVOLVE. Schaeffers, to name a few.   

 

That should handle the how and why. 

 

BTW Exxon/Mobil makes GM's DEXOS licensed oils.

That does not mean however the AC-Delco oil is equal to Mobil 1 AP.  

 

Maybe James or @newdude will show up for the oil pressure questions. They know those years oil system layouts better than I.

GrumpyBear, earlier today I posted a question earlier about Dexos and I had forgotten I posted this post a year ago.  So.....got a question for you.  You mentioned M1 makes the dexos oil for GM.  I didn't know that.  But you also said " that doesn't mean its equal to M1 oil.  Understand that.  Since I'm letting an independent mechanic do my next oil change I'm considering going with M1.....or Castrol synthetic.  Two questions:  (1) With 157k miles on a 2011 5.3 would you stick with Dexos, or would one of those two full synthetic oils be fine if they are not Dexos1?  (2) How do you feel about Castrol synthetic?.