The long-term aging processes during storage of different heating oils and their blends with biofuels including fatty acid methyl ester, hydrogenated vegetable oil, and power-to-liquids products were followed by different analytical techniques, and the aging products were analyzed. While most standard techniques are time-consuming and labor-intensive and specify only a single property, analyses by benchtop nuclear magnetic resonance spectroscopy proved to be effortless and fast. Moreover, only 0.4 mL of the sample is required for nondestructive NMR measurements. White and waxlike precipitates were found in FAME stored at a cold temperature and identified as esters of glycerol with saturated side chains by chromatographic, thermal, and spectroscopic analyses. At colder temperatures, they reversibly precipitate and can lead to system failure.