Oil Evaporation Temperature...

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At what temperature does oil start to evaporate? I am debating oil evaporation with an engine tuner. He is stating that since the bottom-half of the header runs right below the oil pan, that the header acts like a stove boiling a kettle of water. We are talking about Honda engines by the way, which Honda has employed in pretty much every Honda engine that they have manufactured since their existence. Also, he blames the oil evaporating as a reason why Honda engines consume oil consistently. Comments? Oz
 

The_Oz

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quote:
Originally posted by Ken: The newest specs for evaportation call for testing 1 hour at 250C, and limit evaporation to 15% by weight (13% for some ACEA grades). The previous spec (API-SJ) was a max of 22% loss. I'd think that evaporation as you describe would result in an increase in the remaining oil's viscosity? Does that happen? Ken
Ken, What you described is the NOACK volatility. It's a test of "how much" oil lost through evaporation in a given time, instead of the temperature at which oil starts to evaporate. The latter is what I am looking for. Regards, Oz
 
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Under those terms, oil is always evaporating. There is no set temperature where it "starts" to evaporate. So long as the medium (in this case air) above the liquid (in this case, oil) has a lower concentration of oil, then some will always be moving into and out of the air. Granted, at low temperatures, the amount is very low, it is still there, and increases as you increase temperature. That is one of the reasons the NOACK is done at a "set" temperature, besides just for continuity.
 

MolaKule

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The vapor pressure of the oil at a certain temperature would determine how soon an oil starts to evaporate. The lighter fractions or cuts would start to vaporize sooner than the heavier residuls, so for dinos, oil evaporation occurs at different temperatures. Some synths do this too, if they are constructed of different base viscosities, but generally are more stable, thermodynamically.
 
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Most oil loss is not from evaporation but through it slipping past the rings and being burned in the cyls. Usually going to a slightly heavier oil will fix this if the engine is in good condition.
 

driven2services

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The newest specs for evaportation call for testing 1 hour at 250C, and limit evaporation to 15% by weight (13% for some ACEA grades). The previous spec (API-SJ) was a max of 22% loss. I'd think that evaporation as you describe would result in an increase in the remaining oil's viscosity? Does that happen? Ken
 

The_Oz

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Guys, This just dawned on me right now. I remember my work light bulb got coated with a thin layer of motor oil (don't ask me why, it was stupid of me [Dummy!] ). Anyway, I don't know how hot a bulb gets, but it was evaporating the oil until nothing was left. Now, if this bulb generates a temperature lower than 250 Celsius (temp. used for NOACK tests), then is it safe to hypothesize - or better yet, conclude - that NOACK MAY not be a viable test? Comments? Oz
 
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Oz, The reason for running the Noack Volatility test @ 250C is to accelerate the rate at which the oil evaporates. This allows you to generate meaningful numbers in a reasonable amount of time - 1 hour in this case. Oil will evaporate at temps much lower than 250C, but you'd have to run the ASTM test for a much longer period of time. This test does corrolate very well with oil consumption in actual use. Accelerated aging tests are commonly used to look at degradation of polymeric materials. As just one example, the aerospace industry does accelerated aging tests of solid propellant formulations by aging them at elevated temps. This allows you to see how the propellant would degrade after several decades at room temp.
 

The_Oz

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quote:
Originally posted by TooSlick: Oz, The reason for running the Noack Volatility test @ 250C is to accelerate the rate at which the oil evaporates. This allows you to generate meaningful numbers in a reasonable amount of time - 1 hour in this case. Oil will evaporate at temps much lower than 250C, but you'd have to run the ASTM test for a much longer period of time. This test does corrolate very well with oil consumption in actual use. Accelerated aging tests are commonly used to look at degradation of polymeric materials. As just one example, the aerospace industry does accelerated aging tests of solid propellant formulations by aging them at elevated temps. This allows you to see how the propellant would degrade after several decades at room temp.
TooSlick, Then evaporation should not be a concern then with high-revving Honda motors? I blame the Honda oil consumption disease to bad cylinder design, letting the oil get past the rings. Regards, Oz
 
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