AMSOIL OE Synthetic Motor Oil is recommended for vehicle manufacturer-recommended oil change intervals; AMSOIL XL Synthetic Motor Oil is recommended for extended drain intervals of 12,000 miles or a year (whichever comes first) and AMSOIL Signature Series Synthetic Motor Oil is recommended for extended drain intervals of 25,000 miles or one year (whichever comes first). AMSOIL Signature Series Synthetic Motor Oil is formulated with better base oils and more robust additives, allowing longer extended drains than AMSOIL OE or XL Synthetic Motor Oils.