0W-20 vs 0W-40 Fully Synthetic

[Cowpie]

Yeah, there is some truth to the CAFE deal going on.  But that doesn't negate the fact that in most situations a 20 weight oil will still do a fine job of lubrication.    And the gooberment requires an OEM to recommend the same grade of oil that they used in the testing stage for fuel economy and such.  I really don't get all worked up about viscosity.  Many use a 40 weight in heavy diesels, but I have grown quite fond of 30 weight in my heavy diesels.  Folks can use a 20w in these pickup truck motors with little problem, but I would probably still use a 30 weight in them.  I have just found that 30 weight oils cover all the bases very well in a wide variety of motors and applications.  From the Kawasaki motor in my John Deere zero turn mower on up thru the 12.7L diesel in my heavy truck, everything in my stable gets a 30 weight, only the brand and type differs.  

 

And that heavy truck moves up to 80,000 lb of truck and cargo year round on a 30 weight oil.  It now has 868,000 miles on the motor and it uses less oil than most of the pickup trucks on this forum.  No more than 2 qts in 22,500 mile oil changes.

[Grumpy Bear]

0W20 Neither number is the viscosity of the oil. Both are grade numbers. The chart shows the kinematic viscosity (cSt) for each grade at their specified temperatures. You find your particular oils numbers on the data sheets for that oil. For example Mobil 1 0W20's values are 8.7 /44.8, 100c/40c respectfully. Red Line 0W20 is 9.1/48. Take note that the 100 C value for Red Line is only 0.03 cSt from being at 30 grade oil? As hot at they are running these motors, well above 100C/212F oil temperatures the differences are nearly zero within a grade at operating temperatures. Look at high temperature/high shear values for your oil. The viscosity at 150C. 

 

My 262 Ecotec3 V6 calls for 5W30 but has been running 5W20 most of it's 73,000 mile life. About 3 oil changes now on 0W20. It uses no oil. It tosses no codes. My VVT and AFM work splendidly. If fact since the trade to the 0W spec...the AFM works the best it ever has. 

 

I do run a colder thermostat. 180 F & NPG-Ester/PAO oils. (Full disclosure). 

 

Your motor cares little, as far as viscosity is concerned, what the viscosity is on the data sheet on in the bottle. It cares about operating temperature. Your right foot can elevate the bulk oil temperatures 25F without a thought and in seconds.

 

Even in todays motors more parts are lubricated by splash than there are lubricated by pressure. One of the most highly stressed interfaces in the motor, lifter roller to cam lobe, is splash lubricated. If GM can spec a 0W20 and then run the oil temperatures above 235 F in a 5.3 I'm not worried for a second about running it in the 4.3 at 212 F. Nor would I be about running that 40 in a 30 spec motor although I wouldn't personally being a fuel miser and all. 

 

[Cowpie]

True enough the the numbers are a grade, but the numbers on either side of the "w" have no correlation with each other.   The number before the "w" represents the range of cold flow, or CCS viscosity at particular range.   The number after the "w" represents the grade of  kinematic viscosity at 100c.   The operative desire is to use a oil whose CCS does not exceed 6000 at cold start up.  For most folks, the need for a 0wXX oil just isn't there.

 

GM might want a 0w20 to be used, but in most situations a 5w20 would do as well or better and offer a significantly lower NOACK (vaporization or "burn off") loss rate which can be a good thing with DI / AFM engines.   And that is in direct correlation with the greater amount of polymeric viscosity modifiers needed in a 0w20 compared to a 5w20 oil. 

 

I would not use a 0wXX at all.  Ow20, 0w30, 0w40.  No real need and no appreciable benefit.   I only use 30 weight oils, and in all my vehicles from my GM stuff to my commercial semi truck, a 10w30 does just fine.  Matter of fact, my 2006 Cadillac CTS has done and still does fine on a Pennzoil conventional 10w30 even though GM says a Mobil 1 5w30 is necessary.  The Pennzoil 10w30 conventional has a very stout add pack and puts many full synthetics to shame in terms of NOACK volatility.  Even equal to that Amsoil's Signature Group IV PAO.

 

Pennzoil conventional 10w30 NOACK is 4.2 as tested by the Petroleum Quality Institute of America.

 

Amsoil 10w30 Signature 10w30 NOACK is 4.1 according to Amsoil, and their 5w30 Signature has s NOACK volatility of 7.1 as tested by the PQIA.  

 

And the Pennzoil has an add pack that is on par with even the top end Amsoil Signature line-up.  And I can get the Pennzoil conventional 10w30 at my local farm and home store for $17 for a 5 quart jug.   

 

According to PQIA, Royal Purple's 10w30 doesn't even come close at a NOACK of 9.8, which is horrible for a synthetic of that viscosity.  

 

 

 

 

Edited January 6, 2019 by Cowpie

[Eagle68]

They are both are 0 weight oils. Viscosity improves are added to the blend to mimic 20 or 40 weight. As the engine running temperature increases so will she "thickness" of the oil. In time, if you extend your oil changes the oil will start to break down to is original 0.