Is 5W20 still fine for long road trips

[UNC151]

Originally Posted By: 2010_FX4
Originally Posted By: Patman
Originally Posted By: Nick R


Oil is thicker when colder. So theoretically, by running a lower thermostat (Especially with an oil-water cooler) you could get a 30wt oil out of a 20wt.


Nick is correct. To further illustrate it, take your typical 5w20 and it's got a viscosity of around 8.5 cst at 100c (212F) A typical 5w30 will have a viscosity of around 10.5 cst at 100c. But if you've got an engine which has an oil cooler and it keeps that oil at a typical operating temperature of around 195F instead, your 5w20 oil will probably end up having an operating viscosity of roughly 10.5 to 11 cst.

So at what temp does a 5W-20 become 5, 10, or 15 and is there a chart or calculation that shows this?

Also, would this situation not negate any benefits for the reasons that a 5W-20 was specified in the first place? If I am running a 30 grade all the time (when running 20 grade), in the same context would I be running a 40 grade (when running 30)? Seems the "CAFE" benefits would be lost...

I will preface this by saying I am no expert and I am here to learn as much as the next chap. However, after researching this a bit, I am not sure that I can agree that a 20 grade oil is "operating" in a 30 grade when running at a cooler temperature. There are many resources and test data available on the web (not all of them may be as accurate as others), but I could not find an example of 20 performing as a 30 in any of the data.

Here is a chart showing oil viscosity versus temperature (according to the report, these are various brands of oils):

As seen here, even at 160F a 20 grade oil is still operating in a 20 grade, conversely, at 210F both 20 and 30 grade are operating between 10 and 12-13 (most of the
Here is a link to the entire report:
Oil Viscosity

Please share your thoughts about this as I am eager to learn and understand this.

 

[dave1251]

Originally Posted By: ARCOgraphite
Originally Posted By: 2010_FX4
Originally Posted By: ARCOgraphite
That says it all. GM have the data. 20 is just for CAFE and grandma.

I respectfully disagree with this. I "ain't" Grandma and I have heavily loaded my FX4 and pulled from Houston to Cheyenne without stopping (except fuel and bio breaks) and it was 100+ degrees all the way and I drove 70-80MPH while using 5W-20. I have had ZERO issues and my used oil analysis are a testament to that.

I do not know why 5W-20 is pounded on so much--many 5w30 oils shear into a 20 grade anyway so what is the big deal?

I have been running PU from the first OC, but I will soon be switching to Mobil Super and will see how well conventional 5W-20 withstands the heat and load when towing. To the OP; I would not hesitate to run it...

The OP has a engine know for piston slap issues and has a smaller sump than the truck guys. 20 grade with large sump and oil cooler and cold thermostat = 30 grade performance.


I could be wrong but the Mitsubishi piston slap was from the late 90's? Also if it does have piston slap higher visocity oils are just going to dampen the noise from slap not solve it.

 

[JackB1]

May want to read this.
http://www.machinerylubrication.com/Read/518/motor-oils

 

[OVERKILL]

Originally Posted By: JackB1
May want to read this.
http://www.machinerylubrication.com/Read/518/motor-oils


Interesting read.... Also note that it is from 2003.

 

[oldmaninsc]

Originally Posted By: OVERK1LL
Originally Posted By: JackB1
May want to read this.
http://www.machinerylubrication.com/Read/518/motor-oils


Interesting read.... Also note that it is from 2003.

Yes I noticed the 2003 as well.
Plus we all know - if it's on the internet it MUST be true! I'm still wondering when the 5W-20 oil in my 4.6 is going to make the engine explode or self destruct. I'm at 95,000 miles now, so maybe in another 300K or 400K miles!