2-ethylhexyl nitrate (2-EHN) is the most commonly used cetane improver to raise the cetane number of diesel fuel. Di-tert-butyl peroxide (DTBP), when used as a cetane improver, can raise the cetane number of diesel fuel without increasing the nitrogen content. This characteristic is especially valuable in regions such as California where environmental legislation fuel nitrogen limits exist.A no-harm testing matrix determined the effect of DTBP cetane improver on various diesel fuel properties. Nine diesel fuels with a range of physical properties were investigated. DTBP and DTBP/2-EHN blended in diesel fuel were evaluated in comparison to neat diesel fuel and 2-EHN in diesel fuel. In addition, cetane number response curves of DTBP and DTBP/2-EHN compared to 2-EHN were generated.