Although RBP has a good adiditive Amsoil offers one as well if you go with https://www.amsoil.com/catalog.aspx?GroupID=81?zo=1709749 its and ashless, alcohol-free additive that improves cetane up to seven points for increased power and performance in all diesel engines.......You will enjoy the benifits of: reduced operating costs, more complete combustion for better performance, power and drivabiltiy, reduces misfiring during warm-up and at low temperatures..
Let me know if i can help or explain anything for ya!!
Just to add to Donovan's post, I use it in my truck with every fillup along with the Cetane Booster, which adds up to 7 points of cetane to your fuel. I am getting 2-3 more mpg and the truck runs smoother and there is less smoke.