Experiences have shown that grain loss is considerable high due to old combine age in Turkey where 8.6 million hectare grain is harvested. Conventional methods are slow and time consuming. Grain loss sensor and monitor may be used to overcome this disadvantage for quick measurement of grain loss. For this, grain losses were measured using grain loss monitoring system and GPS in two consecutive years (2007-2008) in two different field planted with winter wheat crop using combine harvester at two different age. During the study, different operational parameters were taken into account to assess their effects on grain losses. These were forward speed (for year 2007 3-4-5.5 km/h and for year 2008: 2.5-3.5-4.5 km/h) and three beater peripheral speeds (for year 2007: 28.26-23.55-20.41 m/s; for year 2008: 31.92-28.73-25.53 m/s). Grain losses measured by sensor were compared with traditional measurement method (three quarter meter square method). According to this, with the statistical analyses on grain loss values obtained by conventional method, the effects of harvesters forward speed, beater peripheral speed and forward speed- beater peripheral speed combinations on grain loss values were found to be significant (< 0.0001). In the tests (2007 and 2008), grain loss values were retained maximum as 5.78% and 3.24%, respectively at maximum forward speed and beater peripheral speed. While grain loss values are increased in three quarter meter square method, it is also increased in scale values read from the sensor monitor and vice versa in the points where measurement took place. As these values shown analogy with each other, using GPS and sensor together has shown the potential to track combine harvester performance at the field operations which may allow us to improve existing combine harvester operations and prevention of grain losses by setting combine harvester automatically.