To obtain a dispersant having better durability and more excellent dispersion properties in comparison with a conventional N-containing compound- based dispersant or a metal salt-containing compound-based dispersant for internal combustion engines.

The dispersant for internal combustion engines comprises a copolymer (A) composed of units originated from a 1-10C alkyl acrylate (a1) and a 1-20C alkyl methacrylate (a2) as essential constituent units and satisfies the following items (1), (2) and (3); (1): the unit originated from (a1) is ≥50% based on the weight of the total constituent units and the sum of the units from (a1) and (a2) is ≥90%; (2): the number average molecular weight is 50,000-300,000 and (3): the content of N and S based on the weight of (A) is ≤0.3%.