What is it with DEF?

[Gonzo42]

Just what is the Diesel Exhaust Fluid (DEF) ? What does it do and why do I need it? This is my first diesel and I never heard of it.

[F105]

TucsonJim wrote:
I bought my first diesel truck last year. It uses DEF. It's easy to find, and it is used for Selective Catalyst Reduction. That's a fancy term for pollution control. All diesels use it now, even new big rigs.

It's easy to find in most parts stores, truck stops, and even some gas stations. I get about 1100 miles per gallon of DEF. It costs me about $16.00 for 2.5 gallons at the local parts store. It's even less expensive at WalMart.

Here's a website that can give you some background:
SCR and DEF

Depends on your definition of "new big rigs."

Our 2012 3/4 ton Ram with the Cummins 6.7L diesel doesn't require DEF. But I understand the 2013's and newer do require it.

We were lucky to get it in December 2012.

[1492]

Moved from Forum Technical Support

[TucsonJim]

I bought my first diesel truck last year. It uses DEF. It's easy to find, and it is used for Selective Catalyst Reduction. That's a fancy term for pollution control. All diesels use it now, even new big rigs.

It's easy to find in most parts stores, truck stops, and even some gas stations. I get about 1100 miles per gallon of DEF. It costs me about $16.00 for 2.5 gallons at the local parts store. It's even less expensive at WalMart.

Here's a website that can give you some background:
SCR and DEF