DEF Level Low – Refill Soon

DEF Level Low – Refill Soon


Time start thinking about filling the Diesel Exhaust Fluid or DEF tank.   This is my first truck that uses DEF and I know almost nothing about it.

The truck owners manual says to “Store diesel exhaust fluid out of direct sunlight and in temperatures between 23°F (-5°C) and 68°F (20°C).”   I live in Texas.  It is impractical to  store DEF at 68 degrees or cooler in the summer.  This got me to thinking about DEF shelf life in warmer parts of North America.

I ran across a letter from Ford Motorcraft Chemicals and Lubricants U.S. Catalog to dealers discussing “Conditions affecting Diesel Exhaust Fluid (DEF) Shelf Life and Fluid Quality.”

DEF Shelf Life

DEF, like the milk in the refrigerator, will ultimately go bad.  How fast it goes bad depends on the temperature it is stored at.   This means I shouldn’t buy more than I can use.

The truck owners manual says that if the urea concentrations are low (stored too long or at higher temperatures), the truck will simply use more DEF.

The truck DEF tank is 7.2 gallons.  The truck’s information display shows that we have enough DEF left to go an estimated 457 miles and the truck has 3,127 miles already.  I’m assuming the tank was full when I bought the truck.  I should note that Jordan Ford, where I have bought and serviced all my Fords for the past 17 years, filled the Diesel tank (49 Gallons) on delivery.

Miles per gallon of DEF can be estimated by dividing (457 + 3127) or 3584 by 7.2 which equals 498 miles per gallon (rounded up).

Based on this estimation method, our range on one full tank of DEF is 3,585 miles.

The maximum amount of DEF that will fit in my almost empty DEF tank can also be estimated.  Divide the actual miles driven 3127 by the estimated DEF MPG 497 giving us around 6.3 gallons of DEF to be added to the DEF tank to bring it to full.

I’ve been looking for DEF in truck stops, gas stations and auto parts stores.  I’ve even seen DEF in Sam’s Club.   The only brand I’ve found so far is BlueDEF.  I’ve found it in 1 and 2½ gallon sizes.  The 2½ gallon size comes with a dispensing nozzle which I would need to fill the DEF tank.  I saw BlueDEF in the 2½ gallon size at Sam’s Club for $10.98.

If I want to fill my DEF tank, I’ll need to purchase three of the 2½ gallon boxes.  I’ll have some left over that I can use later but not too much later.


I wish the BlueDEF packaging had a manufacture date clearly printed on the label so I could see how fresh the product is.

Since I’ve heard from friends that Buc-ees has the freshest DEF, I’m considering driving to their New Braunfels, TX location to buy some.

Can I buy DEF in Canada?  Some place remote like Dawson Creek?  The answer can be found on the Discover DEF website by first clicking on the Canada link and then on the Retail DEF Search tab.  Enter Dawson Creek into the search box and submit.  Three Dawson Creek DEF retailers are listed.  Problem solved.



4 thoughts on “DEF Level Low – Refill Soon

  1. The best is to go to a truck stop and fill up DEF just like buying gas. Anywhere you find diesel trucks you should find supplies of DEF at at special pumps.

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