IMO, the constant use of additives is a complete over-kill... I can see where the use on an occasional basis could quite possibly help disperse accumulated water in the fuel. I can see where you might add it to engines up north, especially in the winter time months.
As for two-stroke oil, it is a great troubleshooting tool that is a little more friendly to modern high pressure fuel systems. Definitely more friendly that MMO, used engine oil or trans. fluid!!. . It can be used to troubleshoot an un-ruly FCA. I've used it on a brand new set of CR injectors in a D max to get them to quit sticking while travelling down the highway. .
Used it on a 7. 3 PSD that was 200 miles out of town with unleaded in one tank!!. . ARGH!!!. . Believe me... it HAS its uses...
Persoanlly, I don't believe the fuel mileage claims, unless you are starting out with REALLY crappy diesel fuel. .