As the question states - do VII's in modern oil formulations deplete at a linear rate ? My reason for asking has to do with potentially controling deposits and if my OCI schedule could reduce the amount of VII induced deposits I may potentially ecounter ? The affect of depleted VII's in oil as related to deposits would of course be closely tied to this question . My actual comparison interest is between M1 5W30 and M1 10W30 . *The background on this line of questioning has to do with research indicating a potential link between oil with higher VII's and intake valve deposits in GDI engines . Your thoughts and experiences ?