I mostly got that from listening to Dr. Booth repeat it over & over. The idea is that a properly running engine, with a clean fuel system, should not need any additives. Also, sometimes the additives can leave deposits if used too frequently or in too high a concentration, or at least that's the theory. There is often no measureable benefit in MPG either - if so, something is WRONG and needs to be fixed (IMO). I had been using some Red Line 85+ in each tank, but quit after hearing Doc's mantra, and whaddya know - there was no change in anything when I stopped using it! Good clean diesel, from a popular filling station (one that moves a LOT of fuel daily), is generally the best thing you can feed the car (well, except BioD, but that ain't cheap.)

Again, if you do use additives, I recommend a diesel-specific additive, not a MMO type item... read up on Stanadyne's website for some interesting information. I like their products a LOT but they're not particularly cheap, or easy to buy locally (mail order is OK).