NOACK is how much of the oil evaporates on a hot plate at a certain temperature, right? And flash point I believe is what temp the oil will combust at. Since these both deal with basically how and when the oil is “consumed” at high temperature, do we even need to know both figures? Wouldn’t the oil with the highest flash point also post the best NOACK result? If I want to especially prevent oil burning, then does one figure mean more to me than the other?
Do NOACK and flash point mean essentially the same
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I'll try to answer this with a bit of a silly example.
Water would do quite poorly in a NOACK test since it would all evaporate away quickly at 250C, but it would look fantastic by flashpoint since it doesn't really burn (my understanding is that the molecules would dissociate at extremely high temperatures).
I think any motor oil that gets in the combustion chamber is going to burn given the 600-700C temperatures in there, and you're probably in real trouble in any oil actually involved in lubrication catches fire. I believe there is some correlation between high flashpoint and low NOACK loss, but I think the latter correlates more closely to things that can actually happen in an engine (especially one with a turbo as an extra super hot spot) than flashpoint.
Also be careful to see if the D92 or D93 test method is used to determine flashpoint, that latter tends to give a lower result than the former for a given oil.
Water would do quite poorly in a NOACK test since it would all evaporate away quickly at 250C, but it would look fantastic by flashpoint since it doesn't really burn (my understanding is that the molecules would dissociate at extremely high temperatures).
I think any motor oil that gets in the combustion chamber is going to burn given the 600-700C temperatures in there, and you're probably in real trouble in any oil actually involved in lubrication catches fire. I believe there is some correlation between high flashpoint and low NOACK loss, but I think the latter correlates more closely to things that can actually happen in an engine (especially one with a turbo as an extra super hot spot) than flashpoint.
Also be careful to see if the D92 or D93 test method is used to determine flashpoint, that latter tends to give a lower result than the former for a given oil.
Originally Posted By: Virtus_Probi
I believe there is some correlation between high flashpoint and low NOACK loss, but I think the latter correlates more closely to things that can actually happen in an engine (especially one with a turbo as an extra super hot spot) than flashpoint.
Also be careful to see if the D92 or D93 test method is used to determine flashpoint, that latter tends to give a lower result than the former for a given oil.
This point is the real answer and well said.
NOACK relates to engine performance concerning oil consumption/loss. Flash point relates to shipping and flammability hazards during transport and storage.
Flash point is only used to classify the hazard ratings of products. There are some applications where flash point is a performance property but engine oils isn't one of them.
Yes, flash point and NOACK volatility will almost always correlate, but the actual number of the flash point is pretty meaningless in a properly running engine and using it to compare products would be folly in my opinion.
I believe there is some correlation between high flashpoint and low NOACK loss, but I think the latter correlates more closely to things that can actually happen in an engine (especially one with a turbo as an extra super hot spot) than flashpoint.
Also be careful to see if the D92 or D93 test method is used to determine flashpoint, that latter tends to give a lower result than the former for a given oil.
This point is the real answer and well said.
NOACK relates to engine performance concerning oil consumption/loss. Flash point relates to shipping and flammability hazards during transport and storage.
Flash point is only used to classify the hazard ratings of products. There are some applications where flash point is a performance property but engine oils isn't one of them.
Yes, flash point and NOACK volatility will almost always correlate, but the actual number of the flash point is pretty meaningless in a properly running engine and using it to compare products would be folly in my opinion.
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