This study focuses on developing a convenient method for quantification of ethanol in diesel-ethanol blend and extends the miscibility of diesel-ethanol blends using n-butanol as a third fuel component. Mutual solubility of n-butanol with diesel and ethanol in all proportions makes it a potential fuel additive/cosolvent to overcome the solubility problem. The amount of additive required at different temperatures was evaluated with temperature dependent phase diagrams at temperatures ranging from 10 to 40 °C. Four calibration models were made for both diesel-ethanol and diesel-n-butanol-ethanol blends using a combination of total synchronous fluorescence spectroscopy (TSFS) with two chemometric techniques, unfolded partial least square (unfolded PLS) and multivariate curve resolution-alternating least squares (MCR-ALS). The root mean square error (RMSE) of calibration, prediction, and square of the correlation coefficient (R2) were used to measure model performance in validation data set and reference data set. Prediction ability of both the models was tested by testing diesel-ethanol and diesel-n-butanol-ethanol blends of unknown concentrations. Error of prediction by both the models is found to be less than 2%. Thus, the calibration models for both blends are highly robust and capable of estimating ethanol concentration in diesel. © 2015 American Chemical Society.