What is a good cetane number - and why is it important?


Jan 26, 2023

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For many diesel equipment owners, cetane may be a familiar term, but its meaning remains a mystery. And though cetane may not always be top of mind, ignoring it can prove costly. Running equipment on diesel without a sufficient cetane number can result in rough operation, lost efficiency, excessive wear and more.

Understanding how your equipment works is key to running a successful operation. Read on to learn the fundamentals of cetane and how it can impact your bottom line.

What is cetane?

Simply put, cetane is a chemical compound found naturally in diesel, and it ignites easily under pressure. Because of its high flammability, it serves as the industry-standard measure for evaluating fuel combustion quality.

Specifically, this measure is referred to as cetane number. Think of it like octane ratings on gasoline. The difference is that, while a good octane rating means a fuel doesn’t ignite too soon, a good cetane number means a fuel ignites as soon as possible.

This is because of a fundamental difference in the way gasoline- and diesel-powered engines operate. In a gas engine, fuel is compressed then ignited with a spark plug. A diesel engine, however, doesn’t have a spark plug — combustion occurs through compression alone.

Why do cetane numbers matter?

The higher a fuel’s cetane number, the quicker it ignites — and that carries a variety of benefits for diesel equipment. From increased fuel economy to fewer emissions to better power output, fast combustion is key to a diesel engine’s performance.

The scale for measuring cetane ranges from 0 to 100, and the higher the number, the better. Modern highway, on-farm, and construction diesel engines tend to require fuel with a cetane number ranging from 45 to 55. Typically, regular no. 2 diesel has a cetane number of 40 to 42, while Cenex® Premium Diesel has a cetane number of 47 to 52.

How to boost a fuel’s cetane number

Many diesel equipment owners looking to boost their fuel’s cetane number turn to aftermarket additives known as cetane improvers. Highly combustible, these chemical compounds are designed to make fuels burn more quickly.

The trouble with these aftermarket products, though, is the amount of guesswork they involve — and that makes them inherently risky. There’s no shortage of options on the market, each with their own compelling claims. And often, it can be difficult to tell between a legitimate product and harmful snake oil.


A safer approach to protecting your equipment investment is to use a Premium Diesel with cetane improver already built in. CENEX ROADMASTER XL® and CENEX RUBY FIELDMASTER® are both terminally injected with the optimal level of cetane improver as part of their multifunctional additive package. As a result, they provide a quicker, more complete burn.

When it comes to maintaining equipment, fuel doesn’t need to be a mystery. For enhanced engine performance, the secret is in the cetane. To learn more, contact your local Central Valley Ag Energy Representative. 

Shared with permission from Erin Wroge, Senior Product Manager, CHS Refined Fuels Marketing 

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