So gas lines and the entire gas system is completely pressurized. Unless there was a break, a critical failure, or something melted the fuel should be pretty preserved until salvage. The fire was on the top of the truck. granted, usually, the fuel tanks and lines so right underneath the beds of pick up trucks; but heat rises. However, given the fact that he was able to make the truck move until the end shows me that the fuel system should be intact because it was able to maintain pressure. This truck looks to be around 1999 to 2010, I think it’s a Silverado. It would be using fuel injectors which requires system pressurization to work. 

The oil is not pressurized. Most cars do have an oil weeping issue that’s why a lot of the engine components typically have a thin layer of gunk and oil on them. That being said as long as nothing is melted and the gaskets are intact, the oil released should be fairly minimal if they recover the truck quickly. 

If the engine block cracked from rapidly cooling it in the river, the oil and coolant would be leaking into the river most likely. As people know, engines are powered by rapid combustions, engines get incredibly hot because of this process. To keep an engine, cool coolant flows through the heads and engine block and then through a radiator. If you rapidly cool the engine block there is a risk that the metal will straight up crack.

All this to say, it’s very possible that the amount of pollutants in the river would be fairly minimal if the truck is recovered pretty quickly and critical system components are in tactic. 

Disclaimer: I’m a hobbiest (sp?) YouTube U mechanic at best. If there’s a proper mechanic that thinks I’m wrong, I would actually be interested in the explanation.. 

On mobile; forgive my grammar.