Ash content corrolations to Pre-Ignition

[vex]

This information may be old, but does anyone have anything else to say about it?

I'm reading a paper on Engine oil lubrication for the Rotary Engine (RE), and there seems to be a strong correlation between ash content and pre-ignition events.

For instance an oil that contains <0.05 Sulphated ash % by weight took more than 40 (2.5 hrs run time = 1 cycle) cycles before the first pre-ignition event. For the second run it took 35, for each consecutive run there were no pre-ignition events. Compare that to oils that have relatively high ash contents (1.2, 0.9) which experienced their first pre-ignition event within 8 cycles.

On the market today, how many oils are there that have a lower Ash content similar to the <0.05? Do synthetic oils use base stock with that low of an ash content? I tried looking at Royal Purples website, but they offer no insight on the ash content of their product.