OK. I know next to nothing about Cummings engines. My brother calls me tonight and starts telling that a friend of his, (Dodge Cummings owner) says that he has to add some sort of additive to his gas because of some federal clean air law. And...That his truck has a 5 gallon tank for the additive for automatic mixture. Was this guy yanking my brothers chain???? I believe the truck is a 2007 Dodge. I guess the real question is...Do you have to add anything to your diesel fuel or do you just gas up and go??

 

The fluid is Diesel Exhaust fluid and I am not sure Dodge Cummins needs it but the Ford PowerStrokes do. It is a commercial grade Urea that is sprayed in the exhaust to satisfy the EPA exhaust requirements.
If the brand truck your driving requires it, and you let it run out, the engine goes to limp mode until you fill it up. I thought the prices per gallon for the DEF is just under ten bucks a gallon, but I am sure you can shop around. The government is doing everything to screw up a tried and true engine.

 

dodge just started doin that with there commercial line up (cab and chassis trucks) but i dont know about a 07

 

The only thing I'm thinking of is maybe he's pouring in an additive like Power service, or Stanadyne, or something of that nature. The new Ford and GM diesels do have a DEF tank that must be filled, but currently the Dodge/Cummins uses urea injection on they're C&C trucks only. There is no urea injection on a 2007 Cummins truck. I don't believe they even had a DPF filter yet in 2007.