IMHO the cetane rating of diesel should be displayed at the pump. 40 minimum is not high enough for modern high performance diesels. I've always used additives for my Ram Ecodiesel. Strange that Ram suggests "Power Service Diesel Kleen" for the Cummins, but nothing for the Ecodiesel. Raising cetane and lubricity can't be bad. Been using Hot Shot' EDT mostly, though.
Right, which is why I was questioning what the objective of the OP here is. If you are looking for better MPGs on
every tankful, then you need to use a fuel additive with a Cetane Booster on
every tankful; like the Motorcraft Cetane Booster or combo additives like Stanadyne Performance Formula or Hot Shot's EDT.
I guess using Rislone Hy-per Diesel Additive once every oil change/5K interval is better than doing nothing at all, but as I already mentioned I wouldn't be using this every tankful because of the injector cleaner component, and if you only run every 5K, then you only get the MPG improvement from the Cetane Booster every 5K... I run Stanadayne Performance Formula every tankful, not because of just the Cetane Booster, but rather everything else that the Performance Formula provides -- the Cetane Booster is an extra bonus. For a discussion on what Stanadyne Performance Formula offers, please see this
Diesel Fuel additive recommendations thread
If OP is only concerned with improving MPGs. then I'd look at the Motorcraft Cetane Booster or something like Optilube XPD, which I think is the one "claims" to help with average miles between regens
@Smokewagun = I have never used the Optilube XPD, so I cannot substantiate their claims!