I believe the local diesel shop sells Penray. I know QT’s usually sell soy ( bio ) diesel at least the ones in central Iowa.
I filled up at one by Des Moines a few years ago, may as well of put wicks in my tanks & made candles. out of them.
I may still have a couple bottles of that soy diesel additive.
This is the stuff
Ready for use in BioDiesel. ULSD compliant. Prevents gelling of diesel fuel. Prevents ice crystal formation. Reduces cold filter plug point by as much as 30ºF. Helps enhance cetane. Helps improve fuel economy. Utilizes HAFI® technology. Improves cold-weather starting. Stabilizes and prevents...
penray.com
Penrays other stuff says it works for bio but I had no luck with it.