hi John
welcome to Bio Fuels forums. diesel secret has been discussed b4 on many biofuel sites and has been found to be snake oil. my advise is to stay far far away from it, it is nothing but a scam. to your other question......pay excise on fuel you make well it would be more trouble than it is worth, best thing would be to make it, put it in ya vehicle use it and just keep quiet about what you are doing. The ato requires that you make your bd to atsm standards and to prove that you fuel is up to this standard you are required it get it tested. I believe that the cost of testing is quite expensive. Each batch would have to be tested to ensure that it meets this standard. by doing a search of this forum you will find threads on the pros and cons of paying excise. hope this has been of some help to you.
cheers Fantom.