Method for operating an internal combustion engine

A method for operating a compression ignition engine, the engine having at least one cylinder and a piston moveable in the at least one cylinder, and the method comprising the steps of:

• forming a combustible mixture by mixing generally homogeneously a first fuel and air and introducing this mixture into the at least one cylinder
• compressing the combustible mixture with the piston in a compression stroke
• during the compression stroke but before start of combustion adding a second fuel to the combustible mixture, thus creating a cylinder charge, the second fuel being easier to autoignite than the first fuel
• continuing the compression stroke until combustion starts at those locations in the cylinder where concentration of the second fuel and/or temperature of the mixture is highest,
• wherein a temperature of the cylinder charge, or the amount of second fuel added to the combustible mixture or a combination of both is being chosen such that a desired duration of combustion can be achieved.