Another user on the forum claims using Opti-Lube XPD increased his MPG by 11%:
11% FE improvement with diesel fuel additive
XPD claims to raise cetane by up to 3 points, add lubrication to fuel, remove water and give the fuel anti-gel properties down to -10 F. However, they have another additive to increase cetane higher: "Boost!". It's mostly for raising the cetane rating, in this case up to 7-9 points which is more than other manufacturers I've looked at (Amsoil and Diesel Kleen) claim for their own additives.
Link to Boost on Opti-Lube's site:
Opti-Lube Diesel Fuel Improver | Grease | Oil Fortifier
They have a few other fuel additives for other purposes but I won't talk about them here; what I'm wondering is if anyone else here has tried it and if "Boost!" will increase MPG more than XPD for the higher cetane increase.
Here's a chart rating how well each of Opti-Lube's additives work for what application near the bottom of this newsletter from 2014. (I tried to find something more direct.)
Please do tell what you think.