How Long Does Diesel Last?

Diesel fuel has a wide range of both residential and commercial applications, from powering backup generators to driving large trucks and heavy machinery. Whether you use diesel on a regular basis or only in emergency situations, there are two questions you need to be able to answer in order to keep your equipment running and reduce the risk of fuel spoilage:

• How long does diesel fuel burn?
• What is the shelf life of diesel fuel?

In this article, we attempt to provide straightforward answers to these questions, so you can make smarter decisions when buying and storing fuel.

What Is the Burn Rate of Diesel Fuel?

Different types of engines and appliances burn diesel fuel at different rates. Thanks to both market-driven innovation and increasingly tight emissions regulations, today’s diesel engines are more efficient than ever before. That being said, if you’re not careful, greater efficiency makes it easier to forget to fill up, increasing the risk of running out at a critical moment.

Here are some basic guidelines for accurately calculating the fuel needs of different types of diesel engines:

• Generators: Generators’ diesel fuel burn rates vary according to the size of the generator itself, and to the amount of load being run. A small (20kw) generator may burn as little as 0.6 gallons per hour running at one-quarter capacity, whereas a large industrial generator may require upwards of 150 gallons per hour. It’s important to remember that generators work most efficiently at between 75-100 percent of their rated capacity – running at less than that will cause fuel to burn at a faster rate.
• Vehicles: For diesel vehicles, burn rates are calculated the same as with regular fuel. However, real-world driving and laboratory testing conditions can vary, so take any manufacturer’s mpg ratings with a grain of salt. In general, though, diesel engines are more efficient than regular fuel, meaning less time at the pump. However, since fewer service stations offer diesel fuel, plan accordingly during your trip.
• Boats: Boats and marine engines calculate fuel use in terms of brake-specific fuel consumption (BSFC) – typically expressed in gallons of fuel per unit of horsepower-hour. A boat engine’s BSFC rating will let you know how much fuel is required to keep it running at full power for a given period of time.

How Long Does Stored Diesel Fuel Last?

Diesel fuel has a finite shelf life – using expired or contaminated fuel can lead to premature shutdown or engine damage. On its own, most diesel fuel will begin to degrade at 28 days. This is because the demand for low-sulfur diesel has made most commercially available fuel less resistant to bacteria growth and, as a result, more prone to contamination.

It is possible to extend the shelf life of diesel fuel by using stabilizers, biocides, water controllers and other additives. Many facilities that store diesel fuel for long periods of time will have their supply tested periodically to ensure its viability.

Got a question about diesel fuel burn rates or shelf life? The experts at Foster Fuels can help. Call or email our team today for assistance.

Learn More About Diesel Fuel and Autogas:

• How Do I Check My Diesel Exhaust Fluid Level?
• What is Propane Autogas?