Steve, this is pretty much what I was thinking. To me, it's just like those so-called chips that add 70hp for $69 bucks. I can't tell you how many of my friends have told me that they put this or that chip on their car & now it's running a full second or two faster. I've NEVER seen a chip help anything, whether it's gas mileage or hp but on Diesels! I may be wrong but this has always been my experience!There are very, very few oil additives out there that genuinely do what they say. Zmax isn't one of them.
The additive packages already included in today's oils pretty much negate the need for anything extra. Pick a good oil, pour it in, and call it a day. Wasting brain cells trying to wade through BS advertising isn't worth the time or effort.