1. A method for regulating the ratio between air and fuel during combustion in an internal combustion engine, comprising: burning fuel in the internal combustion engine, the fuel delivered from a tank, checking the exhaust gas of the internal combustion engine with a lambda probe, using a lambda signal from the lambda probe to evaluate a air/fuel ratio, regulating the air/fuel ratio based at least in part on a function of a first adaptation value for the quality of the fuel and a regulation value for the air/fuel ratio, setting a second adaptation value after the tank is filled on the basis of a deviation from a target signal occurring in the lambda signal, when the second adaptation value is applied the lambda signal again corresponds to the target signal, and determining the second adaptation value as a function of the first adaptation value and as a function of a correction factor.