I've been tempted by these emails but I'm falling on the side of it being a waste of money, especially when most branded fuels contain detergents and I pay a premium for VPower for this very reason... I also don't have full trust in Orio since a number of parts have "allegedly" been replaced with Proparts items, instead of alternative quality parts. The valve cover gasket being one example.
I notice they're also peddling an oil system cleaner. Now I have used flushes in the 93, which was a sludge monster when I bought it and my personal opinion was that it was beneficial for that motor, however there's a massive caveat that some oil will always remain when you drain it, thus so will some flush, thus degrading the fresh oil you put in. Unless they're recommending an oil flush to flush the flush, this is dangerous territory IMO..