How do you put DEF fluid in a truck without spilling a drop? Here are a few tips for diesel truck owners out there as well as lots of helpful info about Diesel Exhaust Fluid, what it does and where we found it’s cheapest to buy.
Since 2010, diesel pickup truck engines have relied on Selective Catalytic Reduction technology (SCR), which uses Diesel Exhaust Fluid (DEF), to meet the EPA emmissions standards. DEF is a mixture of 1/3 urea and 2/3 de-ionized water, and it is sprayed into the exhaust system of diesel trucks to reduce the nitrous oxide (NOx) emissions into harmless nitrogen and water.
Each manufacturer designs their trucks with a tank to hold the DEF, and you have to replenish it every so often. Our 2016 Dodge Ram 3500 has a 5 gallon DEF tank. The filler hole is under the gas cap next to the diesel filler hole. On some brands of trucks the filler hole is in the engine compartment under the hood.
As a side note, opening the gas cap on a Ram truck is interesting because there is no screw-on dust cap covering the diesel filler hole inside. There’s just a spring-loaded flap. We find we need to wipe down the whole area after we’ve taken the truck out on four wheel drive roads in dusty places like southeastern Utah.
While it would seem trivial to refill the DEF tank, we struggled the first few times with the bulky jugs and awkward spouts, and it dripped here and there and was basically a pain in the neck.
We’ve also shopped around quite a bit to find DEF that is fairly inexpensive. One of the more common brands is BlueDEF. Others are Command DEF by Prestone and Blue Blood by Cam2. You can also buy it in bulk (see below).
However, the best deal we’ve found is the big blue 2.5 gallon jug of SuperTech DEF sold at Walmart (in-store) for $7.88. The jug is easy to use and it’s drip-free.
SuperTech DEF comes with a flexible pouring spout that is wrapped around the handle. Simply unscrew the jug’s cap and screw the spout on until it’s really tight.
There is a small black vent hole on the spout, and this little guy is essential to making the whole process go smoothly and cleanly.
After putting the flexible spout securely into the filler hole on the truck, give the jug a small squeeze to start the flow of fluid. This will make the vent hole on the jug such air in, which vents the jug and allows the fluid to flow easily.
Make sure all the fluid has been poured into the tank, and then you’re done!
The first time we did this, we didn’t squeeze the jug first, and DEF dribbled out the air vent. But if you get the siphon going properly, by squeezing the jug as you start to pour, it’s a cinch.
Our Ram truck has a dashboard gauge that indicates the fill level of the DEF tank. When it gets down to half full, we put a 2.5 gallon jug of DEF into the tank to fill it back up again. We typically do this every 1,000 miles or so.
DEF has a minimum shelf life of a year. We keep just one 2.5 gallon jug on hand at all times. Since we refill our tank about every four to six weeks, we never remotely approach its shelf life.
Buying DEF in Bulk
Another option for DEF fluid is to get it in bulk at a gas station. This is not common yet, and most gas stations don’t have DEF in bulk. However, Flying J and Pilot truck stops carry it at some of their travel centers (see links at the end for locations).
In our travels, we don’t often fill up at Flying J or Pilot, simply because they tend to be on the interstates and we tend to be on back country roads. So, we haven’t yet seen or been able to take advantage of their bulk DEF at the pump.
However, for RVers that use these travel centers a lot, this is a super way to go. The current bulk Flying J / Pilot DEF price at many of their centers is a little less than the SuperTech bottled price (~$2.79/gallon vs. $3.16/gallon).
Pilot / Flying J offers a discount card for RV travelers that gives a few cents off on fuel and 50% off on RV dump station fees, and special discounts for Good Sam Club members.
What are the pros and cons with a truck that uses DEF fluid? An obvious disadvantage is that you’ve got to do this extra little chore every so often.
However, there are benefits too. The fuel mileage is slightly better on SCR equipped engines than on older trucks that used a Diesel Particulate Filter (DPF) to meet the EPA emissions standards (like our 2007 Dodge Ram 3500). Cummins, manufacturer of the engine in the Dodge Ram line of diesel trucks, says the improvement can be up to 5%.
This increase in fuel economy is because the improved conversion of NOx emissions allows the newer engines to be fully optimized. Also, the older engines go into a “Regen” frequently to burn off the particulates in the Diesel Particulate Filter. In a Regen, a higher quantity of fuel than normal is pumped into the engine to make it run hot so the particulates can be burnt off. This wastes fuel and ultimately lowers the truck’s overall fuel mileage.
The newer engines that use SCR technology (and DEF) don’t need to go into a Regen quite as often.
For more info on all of this, there are lots of links below that explain the history and mechanics behind Diesel Exhuast Fluid.
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More info about Diesel Exhaust Fluid:
- SuperTech DEF sold at Walmart (in-store pickup only)
- Diesel Exhaust Fluid Q&A from Cummins
- Diesel Exhaust Fluid explanation
- Understanding Diesel Exhuast Fluid
- Top 10 Facts about Diesel Exhaust Fluid
- Pilot Flying J Bulk DEF Locations
- Pilot Flying J RV Discount Card Info
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- How to Defrost an RV Refrigerator in 20 Minutes
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- How to Save Space in an RV
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- How to Install a (removable) B&W Fifth Wheel Hitch
- How to Get Phone & Internet Access On the Road (a minimalist solution)
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