Is There Any Environmental Impact On Exhaust Brakes

[Maine farmer]

Our new (2007) farm diesel pickup truck came with exhaust brakes.  I love them for slowing down while saving wear and tear on the brakes, but I wonder if they have any effect on fuel economy or emissions.  Any thoughts?

[CraigD]

I don’t know much about exhaust brakes, or diesel mechanics in general (I’ve never even once worked on a diesel engine) but from what I could tell from a web search, they will slightly decrease fuel use and increase emissions rates if left on when you’re pressing the accelerator pedal.

 

If your foot is off the pedal, the injectors should be supplying no more fuel than needed to run the engine at idle, so exhaust brakes shouldn’t have any effect on consumption or emissions.

 

So bottom line, if you’re careful to switch off the exhaust brakes when they’re not needed (ie any time you’re not going down a long hill), they’re nothing but good, saving on brake wear. Not having to change brake pads, rotors, etc. as often is good for the environment.

 

You could reduce fuel use and emissions to zero when braking going downhill if the injectors closed completely, but I don’t think any stock system does this. I may be wrong – fuel injection systems are pretty complicated, and way outside of my mechanical comfort zone. :confused: