Do to what? Foaming? Now, I don't use a blended oil and I don't just pour Lucas in an unregulated amount into a crankcase that has a huge air gap in it either. I have had zero problems running pure synthetic Lucas (not used by the oil guy) and I have never experienced any foaming at all. My Jeep has been using it for the last 200,000 miles and it still runs awesome and quiet too. Now, I'm not saying the foaming can't happen, only that I have yet to experience any problems with Lucas at all.
Now, as to Bobs test, PVC and Lexan can develop gases when under heated temperatures which can cause foaming on their own. Also is the amount of Lucas that is added to the system as (one must read the directions) or as one guy over on the Mercedes forum found out when he put pure 100% Lucas in his diff, it "will" foam much as many additives will when not used in their respective proportions.
To each there own....