Hiya Paul, as you know I was always a firm believer in using this, but I no longer use it anymore. The car is getting old it's nearly ten now, and haven't noticed any difference in any area at all.
I cannot say long term if did any good before, but nowadays would rather keep my money in my pocket with no visible advantages. This engine after blowing up last one, has now done 120,000 miles, and it didn't seem to help last engine in the end.
Being a conservative driver may be why I don't notice anymore.