I need a quick crash course in terminology pertaining to diesel fuel.... First, what is "No. 2 Diesel"? Are there different grades or names for different diesel fuel types? I know green dyed diesel is on-highway (taxable), and red dyed diesel is off-highway (non-taxable - or at least governed differently). I know I'll run into specific terms while doing my research, so I want to elliminate most questions beforehand. Thanks, ya'll.