In situ formation of ionic liquids (iIL) represents a facile and eco-friendly method for IL synthesis. Here, an oil soluble iIL was prepared by dissolving lithium bis(trifluoromethyl)sulfonylimide (LiTFSI) in glycerol trioleate (Gt), through coordination between the carboxyl oxygen (C=O) group with Li + to form stable and strong Lewis acidic cations. The obtained iIL ([Li(Gt)]TFSI) exhibits high stability in nonpolar hydrocarbon oil - polyalphaolefins (PAO). Tribological test demonstrate that the addition of [Li(Gt)]TFSI dramatically reduces the friction and wear rate of PAO6 base oil at both room or elevated temperature. Surface analyses using X-ray photoelectron spectroscopy (XPS) and focused ion beam–assisted scanning transmission electron microscopy/energy-dispersive spectroscopy (FIB-STEM/EDS) reveal the formation of a tribofilm on the steel surface. The tribofilm is mainly composed of iron–oxygen and iron–fluorine species, with sulfur-containing species locally distributed near the film/substrate interface. The formation of such a tribofilm is associated with the enhanced friction-reducing and anti-wear performance of PAO6.