Investigation of the LTC fuel performance index for oxygenated reference fuel blends

•We describe a previously introduced new fuel performance metric for LTC engines.•Driving cycle simulations provide real-world engine operating conditions.•We modeled HCCI engines to determine fuel operating envelopes.•We calculated the LTC performance index for oxygenated reference fuels mixtures.•The LTC fuel performance index is not well-correlated to octane number.