Getting My Head Around Volatility Numbers.....

[JSRT4]

I've been considering oil volatility numbers recently and I have a few questions on the subject if some of the experts around here could lend some advice. Here they are in no particular order:

Is it worth comparing oils based on volatility numbers ?. If one oil has a higher volatility number I take that to mean that more of it burns off within the engine, correct ?. If so where does the oil go ?, just into vapours ?. Does higher volatility relate to higher oil consumption in an engine ? - i.e. seeping past the rings. Lastly, does an oil with higher volatility have more of a chance of leaving deposits in the engine ?.

Thanks for any replies on this matter.

 

[d00df00d]

One thing I have read is that higher volatility leads to more burn-off in the area of the piston rings, and this can lead to oil consumption and thinner films, but also lower deposit formation.

 

[JSRT4]

Originally Posted By: d00df00d
One thing I have read is that higher volatility leads to more burn-off in the area of the piston rings, and this can lead to oil consumption and thinner films, but also lower deposit formation.


that's what I was concerned with, higher oil consumption, but how does it lead to lower deposit formation ?, when the oil burns off doesn't it leave some deposits behind ?, sorry for any confusion on this.

 

[d00df00d]

Volatility means evaporation. If it evaporates when hot, it can't burn off.

 

[AzFireGuy79]

Im pretty sure its the other way around. Most of the high end POE oils have low volatility numbers and low deposit formation is where they really shine. Granted other factors play into this but I dont know any benefits of a high volatility oil?

 

[d00df00d]

Esters are good at deposit control because of their high flash points, their high solvency, and the fact that they just don't leave much behind when they do burn. Their low volatility numbers are a bonus.

When you're dealing with a group III or IV base, it's a different ballgame. Those have lower solvency and do leave stuff behind when they burn. In that case, higher volatility isn't always a bad thing.

Mind you, I'm not saying high volatility is good. Just that it's a two-edged sword.



EDIT: Wow, just noticed I did something stupid. When I said "burn off" in my first post, I didn't mean it actually burns, just that it vaporizes. My next post must have been confusing because of that. Sorry!

 

[mechanicx]

Wouldn't a higher voltality oil generally have a lower flash amd/or burn point and have the potentional to leave depostis?

 

[d00df00d]

There are three things at play here:

- Whether it burns easily
- Whether it leaves deposits when it burns.
- Whether it cleans up the deposits it leaves.

Esters don't burn as easily, they don't leave deposits, and they clean up after themselves.

Low-volatility group III/IV base stocks burn more easily, leave deposits, and don't clean up as well. Obviously this means more deposits.

High-volatility group III/IV base stocks burn even more easily, BUT they might also vaporize before they even get a chance to burn. So, they can sometimes produce fewer deposits.


The moral of the story is, there's more to it than just the raw volatility number or the general characteristics of a whole class of base stocks. Once again, you have to take the whole formulation into account. Case in point: Mobil 1 5w30 and Pennzoil Platinum 5w30 both meet Honda HTO-06, which is a very strenuous high temperature deposit formation test, and neither of those oils is predominantly ester-based.

 

[JSRT4]

I was concerned with the volatility numbers of the Amsoil 5w-40 AFL I'm running, I find the vol number to be kind of high on decent oil like this, at 8.7 percent. I would have expected Amsoil to produce lower numbers as they seem to criticize Mobil1 and Castrol all the time on volatility numbers despite this formula having just as high numbers as the other guys.

 

[Button]

JSRT4,

ATM 10w30 has the lowest number 5.7. That's the one I chose for my NA Subaru because it was moderately burning SSO.

Regards,
~Button

 

[Gary Allan]

Quote:
I would have expected Amsoil to produce lower numbers as they seem to criticize Mobil1 and Castrol all the time on volatility numbers


I missed this. Can you point me to the marketing/promotional text?

 

[JSRT4]

well on the Amsoil site they have those nice colourful bar charts. Just click on one of their oils and the barcharts appear. They list Amsoil fluids as having low volatility numbers as compared to a dozen other oils, including Castrol and Mobil. But when I look at Amsoil's 5w40 volatility number it doesn't look that great in comparison to their other oils with lower vol. numbers. BTW, I'm running the 5w40 and I like everything that Amsoil has to sell, the 5w40 feels great so far, the engine is very smooth and quiet, and prety strong. I haven't run it long enough to see how oil consumption fares. I'm just curious as to how the 5w40 got a volatility number as high as 8.7. The number on their 10w30 is amazing however.

 

[Gary Allan]

You mean the comparison charts.

Like this one

or this one

All the oils list the numbers.


I just couldn't wrap around "they keep saying".

 

[d00df00d]

Higher viscosity index = higher volatility, all else equal. AFAIK this is a property of both VIIs and the base stocks themselves.

 

[Gary Allan]

Originally Posted By: d00df00d
Higher viscosity index = higher volatility, all else equal. AFAIK this is a property of both VIIs and the base stocks themselves.

Not always

AMSOIL Premium API CJ-4 Synthetic 5W-40 Diesel Oil (DEO)

Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 14.6

Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 87.1

Viscosity Index (ASTM D-2270) 175

CCS Viscosity @ -30°C, cP (ASTM D-5293) 6075

Flash Point °C (°F) (ASTM D-92) 232 (450)

Fire Point °C (°F) (ASTM D-92)246 (475)

Pour Point °C (°F) (ASTM D-97) -46 (-51)

Noack Volatility (DIN 51581) 250°C for 1 hour, % weight loss 9.7

Four-Ball Wear Test (ASTM D-4172: 40kgf, 75°C, 1200 rpm, 1 hr) Scar diameter, mm 0.45

Total Base Number 10.4

High Temperature/High Shear Viscosity, cP (ASTM D-4683) 4.0

Sulfated Ash Content, wt. % 1.0


AMSOIL FORMULA 4-STROKE® POWER SPORTS SYNTHETIC MOTOR OIL SAE 0W-40 (AFF)

Kinematic Viscosity @ 100°C, cSt (ASTM D-445) 14.7

Kinematic Viscosity @ 40°C, cSt (ASTM D-445) 83.7

Viscosity Index (ASTM D-2270) 184

CCS Viscosity, cP @ (-35°C) (ASTM D-5293) 6139

Flash Point °C (°F) (ASTM D-92) 226 (439)
Pour Point °C (°F) (ASTM D-97) -51 (-60)

Noack Volatility, % weight loss (g/100g) (ASTM D-5800) 7.3%

Four Ball Wear Test
(ASTM D-4172B: 40 kg, 75°C, 1200 rpm, 1 hour), Scar, mm 0.35

Total Base Number 10.5

Now M1 0w-40 has a VI of 187 ..but no published NOACK #

Hey, XOM keeps never saying what their NOACK numbers are!!!

 

[buster]

Mobil 1 stopped publishing Noack awhile ago. I think it's around 8-10%.

 

[JSRT4]

Originally Posted By: Gary Allan
You mean the comparison charts.

Like this one

or this one

All the oils list the numbers.


I just couldn't wrap around "they keep saying".


yes that is it. Sorry about the language, I tend to post on here after 12 hour workdays so things don't always come across as logically as I would like. Mean one thing but type another.

At the end of the day I should probably just stop worrying about volatility numbers of my AFL 5w40 and see how the engine likes it with some UOA's in the future. I'm probably putting too much into this one concern. I drive the car so little though that it will take a while to get some data. It sure does feel nice though, the engine has gotten much quieter, smoother, and no apparent loss of power (over 10w30 Castrol Syntec).

Amsoil seems to be a good source of volatility numbers as other companies don't list much info on their websites.

 

[Gary Allan]

I'm sure it's just dandy ..I just was being ..well .. I was just sayin'. j/k

 

[jorton]

Originally Posted By: d00df00d
One thing I have read is that higher volatility leads to more burn-off in the area of the piston rings, and this can lead to oil consumption and thinner films, but also lower deposit formation.


I also read that in Mazda rotary engine discussions. Mobil 1 leaves unburned oil in combustion chambers that form more deposits than conventional oil, because it's less volatile.

Thinner film is okay as long as films in bearings and valve train are not thinned by burn-off.

Amsoil should test the same brands in both charts.

 

[Gary Allan]

It would make a better graphic presentation ..but the numbers are the numbers ..listed on every Amsoil product ..and most others.

I'm rather impressed with GTX in the 10w30 comparison.