Diesel fuel is a petroleum product that, by reducing certain amounts of components, helps preserve the environment but loses the full potential of the fuel. The purpose of this study is to synthesize polymeric additives that improve the low-temperature properties of diesel fuel. A total of six polymeric additives were synthesized through radical polymerization. The reaction was carried out isothermally at 95 °C using 70% Peroxan PO 70 initiator for 4 hours. The polymers have different ratios of long-chain comonomers, octadecyl methacrylate, and dodecyl methacrylate: 1:1, 1:3, 3:1, and different ratios of methyl methacrylate (35%, 45%). Formulations of polymeric additives were prepared at a concentration of 2000 ppm with untreated diesel to investigate the effect of polymeric additives on the low-temperature properties. The purity of synthesized polymers in terms of residual monomers and the confirmed structure of the synthesized polymers were verified using Fourier-transform infrared spectroscopy and proton nuclear magnetic resonance method. According to the FTIR ATR and 1H NMR analyses, the polymer additives exhibit satisfactory purity. More specifically, the initial composition of the monomer mixture approximately corresponds to the composition of the synthesized polymer additive with 0.81% residual monomers. Differential scanning calorimetry was used to determine the crystallization temperatures and enthalpies of crystallization for pure polymeric additives and formulations with diesel. The analysis spectra showed that as the ratio of octadecyl methacrylate comonomer increased, the crystallization temperature also increased, while in the additive formulations with diesel, the crystallization temperature decreased with the increase in the ratio of octadecyl methacrylate comonomer. The morphology of n-paraffin crystallization in diesel was observed using a polarizing optical microscope equipped with a cold stage. A change in the crystals of the 2000 ppm concentration formulation of the polymeric additive MDO35-D5-31 in diesel was observed, with smaller and spherical-shaped crystals. A formulation of diesel fuel with the addition of 2000 ppm additive was performed using the ASTM D5950 method, which showed an improvement in the pour point of diesel fuel with the addition of the synthesized polymeric additives.