What Does Cetane Number Mean?

Cetane number is a measure related to diesel fuel ignition quality. A higher cetane number generally means a shorter ignition delay under the standardized test.

Diesel ignition is different

A diesel engine compresses air until it becomes hot, then injects fuel. The fuel's ignition behavior affects combustion timing and smoothness.

Cetane is not octane

Octane measures resistance to knock in spark-ignition gasoline applications. Cetane describes ignition quality in compression-ignition diesel fuel. Higher is not the same concept across the two scales.

Specifications set minimums

Diesel fuel standards establish cetane-related requirements. Local fuel formulation, season, and additive packages can vary.

Follow the engine requirement

If an engine manufacturer gives a cetane recommendation, use fuel that meets it. Do not assume a cetane additive solves unrelated injector, compression, or emissions-system problems.

Quick checklist

Use the product label, manufacturer directions, and the specific requirements of your situation. Compare the complete product or system rather than making a decision from one marketing phrase, ingredient, or number.