Q: How much DEF will a truck consume?
A: DEF consumption is expected to be approximately 2 to 3% of fuel consumption, depending on vehicle operation, duty cycle, geography, load ratings, etc.
Q: What is the number of miles a truck can expect to travel on one gallon of DEF?
A: DEF consumption is directly related to fuel consumption. A truck averaging 6 MPG can expect to go approximately 300 miles on one gallon of DEF.
Q: Is any maintenance required on the DEF Dosing Unit Filter?
A: The DEF Dosing Unit Filter will need to be replaced about every 200k miles as part of routine maintenance.
Q: How can an operator determine how much DEF they will need/use?
A: DEF consumption will be approximately 2 to 3% of the diesel fuel consumed. Another way to consider it is that DEF will be consumed on a 50 to 1 ratio with diesel. (For every 50 gallons of diesel fuel burned, you will use 1 gallon of DEF). If you know the average fuel consumption of a vehicle, you can easily calculate the amount of DEF that will be used. For a quick calculation, go to www.DEFcalculator.com

Annual miles for average truck = 50,000 miles

MPG for average truck = 8 mpg

50,000 miles / 8 mpg = 6,250 gallons diesel fuel per year

DEF usage @ 2 to 3% of fuel consumption = 125 gallons of DEF / year

125 gallons / 10 gallon tank (average size) = 13 DEF fill-ups / year
Q: Is the DEF dose rate the same for all engine manufacturers?
A: The DEF dose rate will vary slightly amongst engine manufacturers. While most engines will have a dose rate of 2 to 3% of diesel fuel consumed, the dose rate will range from 1% to 3%.
Q: What happens if the vehicle runs out of DEF?
A: Vehicles using DEF will have indicators on the dash that will alert the driver of the DEF quantity on board. A gauge similar to a fuel gauge will indicate the DEF level. There will be a DEF low level warning lamp illuminated when DEF is low. If a vehicle is operated to the degree of running out of DEF, vehicle power will be reduced enough to encourage the operator to refill the DEF tank. Once the tank has been refilled the engine will resume normal power levels.