4 very personalized reasons...
1. charles ledger (the ford master mechanic who runs the yahoo Powerstoke group) told me too...
2. the company that make it ISN't primarily a fuel additive maker (they make fuel injectors)
3. it's the only additive approved by ALL the diesel engine makers (at that time)...
(( and there is an OLD paper on it and all the common additives up to that date which demonstrated the benefits))
4. i did a VERY detailed experiment with the stuff, over 4000 miles in my truck. with it/without it and so on several times, over about 12 tanks of fuel (without additive in between tanks with...)
it CLEARLY increased mpg (lsd fuel) enough to OFF SET the cost factor in MY truck and towing, provided fuel remains 2.50 or more per gallon, so at the 3-4 $ level it really helped with fuel costs.
that data may NOT apply to anyone else or ANY other truck on the planet.
5. i use the performance formula
and buy 64 oz jugs 6 at a time (after the trial phase) from a local shop that will match or better ANY online vendor price.
so for ME it's cuts fuel COSTS a small, but measurable amount. towing 15-20k miles yearly means i'll take any savings i can find.
i also did a long trial with biod. the truck smelled better, but it didn't alter the mpg and the extra fuel filters actually INCREASED my cost factor.