First, the characteristics of the portable electric air compressor：

(1)The portable electric air compressor should be easy to move, have the working conditions which is always changing, and have the big changes of the charge.

(2)The portable electric air compressor belongs to the heavy load, having the rotary of medium speed or low speed, which requires frequent start-up and often bears impact load.

(3)The field environment is harsh, humid, with rock dust, coal dust and gas (the main component is methane), and some harmful gases containing sulfur (sulfur dioxide, hydrogen sulfide), so many mobile screw air compressors have to face fire prevention, explosion protection and corrosion protection problems.

(4) Because of the narrow space, the maintenance of the machine is difficult, so the portable electric air compressor is required to be durable and easy to maintain.

Second, according to the characteristics of portable electric air compressor, the following requirements are put forward for air compressor oil:

(1) The volume of portable electric air compressor and the volume of oil tank are small, so the amount of lubricating oil is small, and the oil temperature is high, which requires that the lubricating oil has better thermal stability and oxidation resistance.

(2) Because of the harsh environment in the field, there are more coal dust, rock dust and water , which makes lubricating oil be unavoidable to be polluted by these impurities, so it is required that lubricating oil should have better anti-rust, anti-corrosion and anti-emulsification performance; when it is polluted, the performance of lubricating oil should not change too much, that is, the sensitivity to pollution should be small.

(3) The temperature of machinery in the open air varies greatly in winter and summer, and the temperature difference between day and night is also large in some areas. Therefore, it is required that the change of the viscosity of lubricating oil should be small with the change of temperature. It is necessary to avoid that  the viscosity of oil becomes too low to form a lubricating film when the temperature is high,, which can not play the role of lubrication. At the same time, it is also necessary to avoid that the viscosity is too high to make starting and running difficult when the temperature is low.

(4) For some portable electric air compressor, especially in the environment prone to fire and explosion accidents, some machines require to use lubricants of good fire-resistant (fire-resistant fluids), and can not use flammable mineral oil.

(5) Require lubricants to be well adapted to seals so as not to damage them.