NOACK measures evaporative losses which I thought were linked to IVD?I'd say B, is there any actual correlation of NOACK to IVD, I thought most of the oil that finds it's way into the PCV and gets burnt onto the back of valves is caused by oil mist created in the crankcase not high temperature evaporation.
Great suggestion. However, according to the Castrol's website, Castrol Edge 5W30 black bottle has .78% SA. Wouldn't that fall under Mid-SAPS?Some people like to try and make that correlation but it has not been proven to be correct. A low SAPS oil such as Castrol Edge 5W-30 is formulated for this issue.
Gokhan wrote a lot about this topic. I came away uncertain. Lubrizol was the originator or marketer of Low SA = lower IVD's. But many have disputed that claim.
There is a lot of chemistry in a bottle of oil so it's very difficult to say unless there were tests developed specifically for IVDs. I've seen that LZ study before as its been posted many times here and other sites.
Oddly enough, Valvoline's Modern Engine oil had a slightly higher Noack than their standard synthetic, which to me suggests it is more than Noack and involves other chemistry to reduce IVDs.
Some have suggested oils with selected ester types or higher concentrations of POE can help mitigate IVD's being they are good solvents. So when the oil vapors or mist come in contact with the IVD it can clean them.
I believe there was something unique with Valvoline Modern Engine. It smelled different and had a significantly higher price tag, which honestly was probably due to the advanced chemistry they were using in it to achieve the results they claimed. It was poorly marketed though and overpriced for the glorious Walmart shoppers who would run to China to save $.10 qt on oil.