With the implementation of the “Worldwide harmonized Light duty Test Procedure” (WLTP) and the highly dynamic “Real Driving Emissions” (RDE) tests in Europe, different engineering methodologies from virtual calibration approaches to Engine-in-the-loop (EiL) methods have to be considered to define and calibrate efficient exhaust gas aftertreatment technologies without the availability of prototype vehicles in early project phases. Since different types of testing facilities can be used, the effects of test benches as well as real and virtual vehicle operators have to be determined. Moreover, in order to effectively reduce harmful emissions, the reproducibility of test cycles is essential for an accurate and efficient application of exhaust gas aftertreatment systems and the calibration of internal combustion engines.In this paper, the influence of different human drivers on the particle count of a passenger car with a small turbocharged three-inline-cylinder gasoline engine with intake-manifold fuel injection is presented. Furthermore, the effects of one human driver in comparison to a virtual driver regarding the reproducibility of the test results are shown. In this setup several particulate measurement systems with different measurement principles are taken into account to validate the results.In the second part of the paper, including the same engine and measurement systems, the effects and influences of seasonal RON 95 gasoline fuel qualities (winter and summer) on the size distribution (5,6-560 nm) and the particulate count are discussed. With the introduction of the Euro 6d emission standards, there is no longer a legal specification in place for the fuel to be used for RDE emission testing. Hence, it must be considered that due to seasonal climate changes, specifically designed fuels are sold at regular gas stations. Although summer and winter fuels are supposed to guarantee the same physical properties, they differ in composition which can lead to considerable differences in particulate emissions. To avoid a mixing of the different climate-dependent fuel types during the test program, the fuel tank has been extensively flushed before refilling it with the next test fuel. As prescribed all fuels were bought at public gas stations and have been analyzed by a third-party laboratory to guarantee the immaculateness of each fuel type.