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.

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

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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 DEFDepends 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.

By "big rigs", I'm refering to commerical tractors such as Freight Liner, International, etc.

The way it came to the market by engine was based by how many engines the engine manufacturer produced. Ford was one of the first as they make few diesel engines by the numbers. (mostly for their pickup line.) Cummins was able to hold off as they made quite a number of engines. Think about the pickups as well as the over the road trucks. They are also big in the industrial line like marine, generators, well pumps etc. So in the big picture it was something that the federal government phased in by mandates. Engine manufacturers had to make a certain percentage of their production line meet the mandate. With that said, it is a far more efficient way of meeting the emission standard than some of the other ways that were previously used. It is by far a less power robbing way of doing the same thing.Further, there are FleetPride truck part company's across the united states selling that DEF for around $10.00 or less per two gallon container. It does pay to shop the product. Don't spill it as its nasty when it dries.

What is it with DEF? | Good Sam Community

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Moderator
Feb 05, 2014
Moved from Forum Technical Support
TucsonJim
Explorer II
Feb 05, 2014
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

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What is it with DEF?

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