Have read in recent times that Noack is :
* meaningless, as your engine oil never gets to 250C and sits there for an hour (multiple times);
* not relevant for xW-20 oils as they run so cool;
* not relevant as catch can deposits are oil mist, not light hydrocarbons.
Major problem with all of these arguments is that volatility tests are there to assess the behaviours of oil that's left above the top ring, hot, and washed by air/gas flow within the cylinder.
These films, and the vapours that are released have direct access to the catalyst on the exhaust stroke, and therefore have relevance, particularly for emissions system performance.
* meaningless, as your engine oil never gets to 250C and sits there for an hour (multiple times);
* not relevant for xW-20 oils as they run so cool;
* not relevant as catch can deposits are oil mist, not light hydrocarbons.
Major problem with all of these arguments is that volatility tests are there to assess the behaviours of oil that's left above the top ring, hot, and washed by air/gas flow within the cylinder.
These films, and the vapours that are released have direct access to the catalyst on the exhaust stroke, and therefore have relevance, particularly for emissions system performance.