Modern low NOx domestic oil and gas burners use the effect of flue gas recirculation to lower combustion temperature and hence to reduce the amount of NO being formed. Because these burners do take flue gas from the combustion chamber and mix it with primary air, a strong interaction is possible between the burner and the boiler. This interaction has to be taken into account particularly for the jet pump type of flue gas recirculators, because it can lower the rare of recirculation and hence increase the NOx emissions drastically. Numerical simulations (CFD) of the oil combustion process within a commercially available domestic burner have been carried out. Extensive comparison with experimental data (LDV, PDPA, LIF, probe) shows the achievable accuracy of numerical simulations for such complex geometry＇s nowadays. The final discussion gives reasons for the differences between simulations and measurements and shows the necessariness of further developments concerning the oil model.