Antioxidant additives are commonly used to prevent biodiesel oxidation. Most antioxidant studies have focused on the effects of chemosynthetic antioxidants, but there has been limited research on natural antioxidants. In this study, a cheap and readily available natural antioxidant, Pyrola extract, was applied for biodiesel protection. An immersion test that exposes biodiesel to copper chips was used to compare the antioxidant activities between Pyrola extract and the commercial antioxidants, pyrogallol and BHT. Pyrola extract performs much better than pyrogallol (PY) and BHT on all of the quality characteristics of biodiesel, including acid value, iodine value, peroxide value, and corrosion rate of the coppers. Analysis by gas chromatography also indicates that Pyrola extract helps to maintain the original components of the biodiesel. Due to the simple extraction process and low cost raw materials, Pyrola extract may be a potential antioxidant for protecting biodiesel. (C) 2019 Elsevier Ltd. All rights reserved.