Starting compressor is the main equipment in the Gas Engine Power Plant (GEPP) that works to produce compressed air needed to start the gas engine. The starting compressor used is a reciprocating type that consists of two levels of compression: the low-pressure (LP) side and the high-pressure (HP) side. In the starting compressor at Arun GEPP, there is a frequent problem regarding the excessive deposit growth rate that clogs tubing in the HP air cooler and compressed air delivery line, thus decreasing equipment reliability. This excessive deposit growth rate is derived from burned lubricants in the HP side compression chamber, which is necessary to increase the cooling capacity of the LP air cooler. Increasing the cooling air velocity is one way to solve the problem. A numerical study is used to determine the effect of variations in cooling air velocity on compressed air temperature in the LP air cooler. Then, it is used to calculate the working pressure limit on the starting compressor to avoid an excessive growth rate of deposit. The results of this study indicate that increasing in cooling air velocity up to 218% was able to reduce the compressed air temperature by 3.57 ℃ and increase the delivery pressure limit of the reciprocating compressor by 1.82 bar.