Originally Posted by edhackett
Originally Posted by Gokhan
Originally Posted by Gokhan
Originally Posted by Garak
For the extrapolated values, that won't hold.
OK, rather than opposing everything without doing any calculation yourself, why don't you extrapolate the KV100 from the KV40 and KV80 values in the above table and then see if it holds or not?
It actually takes only a minute or two. All you have to do is to stick the values in:
https://www.widman.biz/English/Calculators/Operational.html
The answer is, yes, the extrapolation works. You get similar results to what Shannow got for the interpolation.
I'm not too worried about ASTM D341 being applicable to finished oils with VII and DI or not. It's one of the better tools we have. The data here seems to confirm it.
This study was base oil and VII only. The chart holds because VI improvers are hydrocarbons, thus ASTM D341 applies. You can't use this data to prove it works for fully formulated oils, which are not hydrocarbon fluids. ASTM D341 specifically warns that non hydrocarbons do not respond linearly. We don't have a clue what the effect of the multitude of combinations of non hydrocarbon components used in any specific oil fully formulated oil might have on an extrapolated number.
Without measured KV150 numbers you can't even begin the process of empirically validating your equations.
Ed
Hi Ed, you're overinterpreting things.
Exact wordings from ASTM D341:
"It should also be emphasized that fluids other than hydrocarbons will usually not plot as a straight line on these charts."
The way I would interpret it would be "Don't expect it to work it for any fluid" rather than your interpretation "We have this nice oil tool but don't expect it to work if the oil is a finished oil."
I would worry more about the VIIs' effect, which greatly modify the viscosity. The fit function isn't supposed to work well when there are hydrocarbon phase transitions, which is what the VIIs go through in order to modify the viscosity. Therefore, what you said about the hydrocarbons always fitting nicely is also an overinterpretation. Now, you're worried about the DI pack, which has a much smaller effect on the viscosity and should easily be absorbed into the coefficients of the fit function?
Also, if ASTM D341 is completely useless for finished oils, why in the world do they bother documenting the viscosity index (VI) in the PDSs for virtually every finished oil? The viscosity index is based on ASTM D341.
Yes, like every approximation, there is an error in ASTM D341, which varies with the oil and additives. However, to say that it's useless for anything other than pure (neat) base oils is a stretch.