What's the point of oil grades like 5w-30 or 10w-30 or 15w-40? Why not just use 0w-30/0w-20/0w-40 when possible? I've read and searched but could never find a definitive answer
If all oil is too thick when cold...
- Thread starter SnowDrifter
- Start date
I don't know if there is a lot of difference in a 0w30 and a 5w 30 above freezing. I've always thought that it would be more useful to have cst numbers for 0c as well as 100c, verses 40c and 100c.
Nick1994
$100 site donor 2023
I guess the 0w oils shear to a lighter weight oil easier, not quite as stable but getting better.
Originally Posted By: SnowDrifter
What's the point of oil grades like 5w-30 or 10w-30 or 15w-40? Why not just use 0w-30/0w-20/0w-40 when possible? I've read and searched but could never find a definitive answer
0w-xx reminds me of Subaru's 'Partial Zero Emissions Vehicle.' You can't have a partial 0. I don't dig into numbers for flow rates and such, but i'm just not going to run a 0w oil in anything unless the manufacturer state to use a 0w oil.
All lubricants are a compromise, and the compromise comes in different areas.
e.g.
* a 15W40 will generally have a higher HTHS, and be more shear stable (temporary and permanent shear) than a 0W40.
* a 0W40 starting at -25C is a cakewalk, versus the 15W40 that will be struggling to pump at those temperatures.
* 0W40 will not thicken as much below operating temperature as the 15W, and return slightly better average fuel economy.
* 15W40 will likely be less volatile.
* And the 0W40 is undoubtedly more expensive than nearly every 15W40.
Similar arguments for all the other grades.
<span style="font-family: 'Verdana'">So therefore if you're living in Texas, Arizona, or California, 15W-40 will do just fine.</span>
And even Texas - such as the Panhandle and Davis Mountains . . .
My last truck (a 5.9L or 360 V8) spec'd either 10W-30 or 5W-30 based on expected ambient temperature during the OCI (both minimum & maximum).
In Ohio, I ran 5W-30 about half the year and 10W-30 about half the year.
In Southeast Louisiana, I ran 10W-30 year-round.
This is a robust engine design that had been manufactured for decades with decades of experience on its service life. If the manufacturer had seen an advantage at the time of its production to switch to some 0W-XX oil, including CAFE effects, I'm confident they would have spec'd things differently. Others may not be so confident.
I sold it earlier this year with 154,000 miles on it running strong and zero lubrication issues.
Kestas
Staff member
As I understand it, vaporization starts to become a significant factor for 0W oils. That's why most of these oils are synthetic.
Also, going from 10W to 5W "buys" you about 16 degrees F to get the same viscosity. I'm not sure how much more temperature you'll buy going to 0W.
Originally Posted By: Kestas
As I understand it, vaporization starts to become a significant factor for 0W oils. That's why most of these oils are synthetic.
Also, going from 10W to 5W "buys" you about 16 degrees F to get the same viscosity. I'm not sure how much more temperature you'll buy going to 0W.
Originally Posted By: BrianC
0w-xx oils will flow faster and provide less resistance upon cold start in all climates.
Because not all oil is "too thick" when cold. It's just much thicker than it needs to be. The API defines "too thick when cold" as 60,000 cP at their defined temperature setpoints for the various W-grades in the Cold Pumpability test.
Originally Posted By: Shannow
Originally Posted By: BrianC
0w-xx oils will flow faster and provide less resistance upon cold start in all climates.
In all climates 0wt oils will flow faster through the engine on cold engine start than there 5-10 wt counterparts. Here is a video from M1 on the subject. Scrool down to the 0wt video.
http://www.mobiloil.com/USA-English/MotorOil/Videos/Videos.aspx
And this means what in the instances of cold start where there isn't any propulsion load on the engine?
Or do what I do... I use oil pan heaters on all my vehicles and equipment. 15w40 flows, at cold startup, like a warm summer's day. And that is even at -30F which I experience a few times in the upper midwest winters.
Quote:
If all oil is too thick when cold...
Quote:
0w-xx oils will flow faster and provide less resistance upon cold start in all climates.
How do they flow faster...?
The positive displacement oil pump ensures that the same volume of oil is shifted per revolution, regardless of viscosity...
Originally Posted By: Ken2
[quote]
So, why not use all 0W-x oils? Cost, mainly. If the 0W-x oils can be made without excessive viscosity index improvers (which do not lubricate, they just take up space in the oil), then they probably work fine.
Used to be you could just put a tiger in your crankcase
http://www.youtube.com/watch?v=v2TnN_bcoRw
I don't recall ever seeing any 0W-XX Superflo, but none of the vehicles I've owned were ever spec'd for 0W-XX oils by their manufacturers, so it's not something I would have sought.
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