A grease composition contains a mixture of a lubricating base oil, an ester-terminated polyamide and at least one polyolefin. The ester-terminated polyamide has the formula: R1-O—CO—R2-CO—[NH—R3-NH—CO—R2-CO]n-O—R1. R1 contains 4-22 carbon atoms, R2 contains 4-42 carbon atoms, R3 contains 2-9 carbon atoms and n is an integer in the range of 1-20. The grease composition can be used for lubricating a mechanical component having a metal surface and/or for protecting a mechanical component having a metal surface against corrosion, wear and/or fretting.