I was in another forum (Jeep Liberty Diesel) and someone remarked all diesel engines have a return fuel line from the engine to the tank, which always mixes any additives like PS.

1. Is this a true statement?

Thanks much-always trying to learn.

 

Yep they have a return line.

 

Yes, our trucks have a return line to the tank.

Look at the top driver's side of the fuel bowl. That is the fuel return outlet that leads from the fuel bowl back to the tank. Inside of that housing is also the fuel pressure regulator.

If you look at the bottom driver's side of the fuel bowl, that is the fuel inlet line. The lines that feed the heads are on the passenger's side of the fuel bowl.

 

I think driving in traffic for 10 minutes is enough to make any amount of fuel mixed up and entrained with air.