DEF Usage

One of the things I do as I drive the Fuse is to check the Transit Information Messages when we start out in the morning.  I also check it after I fill up with diesel.   As we were coming home from our latest trip to Disney, I checked the info screen and I saw the "DEF level under 1/2 full" message.    No panic, but since we were only a couple hundred miles from the house I put "add DEF to the Fuse" on my to do list.

If you are interested in what DEF is or how to add it to your Fuse, I wrote an article on adding DEF a while back.  But basically it is a fluid that is used by the diesel engine for emissions treatment.

A number of new diesel owners get nervous about DEF and ask numerous questions.  To put people at ease, here are some of my observations after 15,000+miles on my Fuse.

I only add DEF to the DEF tank when the Fuse tells me to.   I do it when the Information screen says "DEF Level under 1/2 full".

When I see this in the info screen I add a 2.5 gallon container to the DEF tank.  The DEF tank holds 5.5 gallons so this is about perfect.

Walmart sells DEF in a 2.5 gallon container with a fill nozzle.  This meets the SAE requirements so everything is good and it costs less than $10.00.  But DEF is DEF like diesel is diesel so use the DEF you are comfortable with.

I do not carry extra DEF in the FUSE.  DEF goes bad over time (several years) and the heat in Florida makes the breakdown go faster.  I buy fresh when I need it.  You can find DEF almost everywhere.  Given the preponderance of big diesel trucks in rural areas it is easier to find out in the boonies than in big cities.  You can find it at truck stops, Walmarts, auto parts stores and most any gas stations that have diesel fuel.  Just get some that is fresh.   Truck stops have DEF pumps if you want to go that route.

The big question is how often do you have to add more DEF to the Fuse?  Well in 15,000 miles I have added DEF 4 times.   I added within a couple hundred miles of seeing the DEF message.  I added at:

• 4,083 miles
• 7,728 miles
• 11,856 miles 
• 15,358 miles

So roughly I added 2.5 gallons every 4,000 miles.   Make sure to use the info center and not what I just told you.  The engine will need different amounts of DEF depending on conditions just like with fuel.

And once you add the DEF.  Wait a couple on minutes.  You get a different message.  DEF level Okay.