This paper was to study whether un-preheated blends of palm fatty acid distillate (PFAD) with commercial high speed diesel (CHSD) without adding any solvent to improve cold flow property could be used as a diesel substitute. In this work, PFAD-CHSD blends, 0-100 wt% with 10 wt.% interval, were prepared by simple splash blending; their long-term phase behaviors at room temperature were observed; and, for the blends of interest, their important fuel properties were tested and their comparative use in a single cylinder diesel engine without preheating was evaluated at 2200 rpm with loads of 1.28-5.09 kW. Although PFAD had poor cold flow property, long-term stable liquid blends of PFAD <10 wt.% could be prepared. According to Thai standards, almost properties of these blends were suitable to use as a diesel substitute except acid values but their copper strip corrosions were similar to that of CHSD, No. la. The 5 and 10 wt.% PFAD blends were able to operate the tested engine in the same manner as CHSD with comparable performance, significantly lower smoke, slightly lower carbon monoxide, and significantly higher nitrogen oxides. In conclusion, the blends (PFAD <10 wt.%) are recommended to use as a simple cost-effective diesel substitute. (C) 2018 Elsevier Ltd. All rights reserved.