Nanofillers are additive materials that fall under the umbrella of nanomaterials, i.e., either one of their dimensions is in the 1–100 nm range. There are many advantages that are carried out by nanofillers themselves, like thermal stability, a higher surface-to-volume ratio, better mechanical properties, good barrier properties, and many more. Nanofiller-based materials are finding their way into the oil, lubricants, and fuel industries because of their better properties than the conventional additives. They improve the rheological properties of fuels and lubricants, improve fuel quality, provide extra oxygen for complete fuel combustion, act as catalysts for better chemical reactions, and improve the quality of emissions from fuel combustion. Some of the common nanofillers for fuel are oxides of magnesium, aluminum, and cobalt. As in the lubricant industry, nanofillers with their better thermal properties help to carry away the heat generated during rubbing and attrition, which helps to maintain the viscosity, ultimately leading to less friction and wear. Other than these mentioned broadly, nanofillers have many more applications in the fuel and lubricant industries, which are discussed in detail in the following chapter.