In general, diesel engines are extremely durable and can last for hundreds of thousands miles with the proper care. But over time, even the most well-looked-after diesels will start to lose power and efficiency. Why is that?
Jason Fenske of Engineering Explained headed over to a third-party test lab used by ExxonMobil to answer that very question. Although there are a few different reasons why a diesel engine can lose its oomph over the years, Jason discovered the biggest problem has to do with fuel injectors.
Unlike gas engines, which use a spark to ignite an air-fuel mixture, diesels (mostly) rely on compression for fuel ignition. In order to get the best explosion possible, diesels use extremely high pressure injectors that squirt fuel into the cylinder via a series of tiny holes. The combination of high pressure and the small fuel outlets creates a mist of diesel fuel that disperses evenly in the cylinder, allowing for a cleaner and more efficient burn.
But over time, carbon can build up on injectors, causing an engine to run less efficiently because it’s not getting the proper mist of fuel. This phenomenon can not only reduce fuel mileage, but also increase an engine’s emissions.
The solution for restoring a high-mileage diesel back to peak efficiency is to use some kind of additive to scrub the carbon deposits from the injectors. In Jason’s case, he examined how ExxonMobil’s Synergy Diesel Efficient Fuel can be used to improve the health of a diesel engine. He found that ExxonMobil’s new diesel tech—which features a proprietary blend of additives—was able to clean up an old diesel to the tune of a 2 percent improvement in both fuel economy and CO2 emissions. Lab results also showed an 11 percent improvement in NOX emissions.
So if your diesel engine isn’t running like it used to, be sure to start with a good cleaning of the injectors.