The growing demand for more economical and environmentally friendly power generation forces the industry to search for fuels that can replace the conventional fossil fuels. This has led to significant developments in the production of alternative fuels during the last years, which have made them a reliable and relatively efficient source of energy. One example of these alternative fuels is the pyrolysis oil. However, higher viscosity, lower heat content, limited chemical stability, and its ability to create sediment make pyrolysis oil challenging for gas turbines. The OPRA OP16 gas turbine is an all radial single-shaft gas turbine rated at 1.9 MW. The all radial design, together with the lack of intricate cooling geometries in the hot section, makes this gas turbine suitable for operation on these fuels. This paper presents an experimental investigation of pyrolysis oil combustion in a tubular combustor developed, especially for low-calorific fuels. The experiments have been performed in an atmospheric combustion test rig, and the results have been compared to the results obtained from ethanol and diesel combustion. It was found that it was possible to burn pure pyrolysis oil in the load range between 70% and 100% with a combustion efficiency exceeding 99% and without creation of sediments on the combustor inner wall. It was found that the NOx emissions were similar for pyrolysis oil and diesel, whereas the CO emissions were twice as high for pyrolysis oil. A comparison between the air blast nozzle and the pressure nozzle was performed. The air blast nozzle was found to be more suitable due to its better performance over a wider operating range and that it is more resistant to erosion and abrasion. It was found that the maximum allowed droplet size of the pyrolysis oil spray should be about 50–70% of the droplet size for diesel fuel.