Interaction between thickener such as polyethylene glycol (PEG) and glycol antifreeze such as ethylene glycol (EG) was investigated by measuring the friction coefficient and the contact angle of the mixed solution of polyethylene glycol and ethylene glycol. The friction coefficient of undiluted EG was larger than that of undiluted polyethylene glycol with molecular weight 400 (PEG400), and the friction coefficient in the mixed solution of PEG400 and EG was expected to increase with an increase in the content of EG added to the mixed solution. However, the friction coefficient of the mixed solution at a sliding speed of 0.05 m/s showed the maximum value at EG content 70 mass%. The contact angle of the mixed solution of PEG400 and EG at 40°C increased with an increase in the EG content in the lubricant on the unheat-treated metal plate, but showed the maximum value at EG content 60 mass% on the metal plate which was heat-treated for 10 min at 190°C and then was cooled at room temperature. The agreement of both the EG content dependences of the friction coefficient and the contact angle might be explained by the intermolecular interaction between PEG400 and EG molecules which was induced on the metal oxide surface.