Try our re-instated info resource - "Aladdin's Cave" (Main menu)- sorry it's taken so long to fix
AFAIK and this is only my understanding of it but Hydrogen replaces the fuel the engine uses as standard, whether it's compatible with Diesel engines I have no idea. They kept commenting on the only thing coming out of the exhaust is water not Co2 so that led me to suspect the engine is still in place.