Engine Braking - Legal Implications

Legal Implications

Engine braking is a generally accepted practice and can help save wear on friction brakes. It's even used in some motor sports to reduce the risk of the friction brakes overheating. Additionally, most modern engines don't use any fuel while engine braking which helps reduce fuel consumption. This is known as DFCO or Deceleration Fuel Cut-Off and is used with Burn and Coast.

Although being phased out from road traffic, there are still plenty of carbureted engines in service, on the most of which engine braking is counter-productive to fuel economy due to the lack of a DFCO mechanism. With increasing fuel prices, the loss in wasted fuel can well outweigh the gain from saving mechanical brake parts.

Compression-release ("Jake") braking, a form of engine braking used almost exclusively on diesel engines, produces extreme amounts of noise pollution if there is no muffler on the intake manifold of the engine. Anecdotally, it sounds similar to a jackhammer, however the loudness is between 10 and 20 times the sound pressure level of a jackhammer. Numerous cities, municipalities, states, and provinces have banned the use of unmuffled compression brakes, which are typically only legal in roads away from populations. In Australia, traffic enforcement cameras are currently being tested that automatically photograph heavy vehicles that use compression braking.