In the petroleum industry, the implementation of new methodologies requires a validation procedure in order to guarantee compliance with the specifications. This study presents a comparison between the methodology proposed for the determination of the API gravity using a gas pycnometer with a standard and an internationally recognized method such as the one described in ASTM D1298. One of the main advantages of the gas pycnometer technique is related to the use of a hydrometer, which requires a minimum amount of sample. This makes it an ideal method to monitor API gravity in research laboratory-scale processes. In addition, it is a simple and reasonably fast methodology for small samples and therefore attractive for processes with limited sample availability like biotechnological applications. Although the validation parameters reported in the literature are varied, only the results obtained by using the new method as compared with those obtained by using the standard methodology, such as those related to precision and accuracy, are presented. For the API gravity values obtained by using gas pycnometer to be equivalent to the results obtained by using the ASTM D1298 standard method, which would allow the use of both methodologies without this resulting in a deviation of the API gravity specification value of the sample, it is necessary to carry out a correction using the linear correlation data obtained. However, taking into account the precision data, reproducibility limits specifically, both methodologies are comparable.