Gas turbine compressor fouling is a major operational issue that affects engine performance. In desert oil and gas, field compressor fouling can be caused by pollution such as airborne ash, smog, hydrocarbons and dust. Accumulation of such pollution in the compressor annulus can lead to sticky fouling. This can ultimately result in the reduction of the compressor mass flow and pressure ratio. In order to maintain constant output power, it is then necessary to increase the turbine entry temperature (TET). The result of such an operational change will cause higher emission rates. In addition, it will decrease the creep life of engine hot components and overall engine thermal efficiency. The investigation of the effect of compressor on-line cleaning leads to the following findings: (i) Frequent cleaning maintains longer creep life of the high-pressure turbine. (ii) More financial benefits due to reduction on fuel flow. (iii) Less cost of cleaning materials per engine, cost of manpower and overheads. In summary from cost aspect with the best frequency of washing intervals (4 weekly), approximately $ 30,000 will be saved annually. On the other hand, in order to attain better engine performance, a weekly washing interval is necessary.