Rinse two oranges and lemons in hot water. Peel and slice the peels into small strips. Peel the oranges, fillet and chop. Squeeze the lemons and measure out 200 ml (approximately 1 cup) of juice. Peel the mandarins and crush, thereby removing the seeds.
Mix the peels, fruit pieces, lemon juice and jam sugar. Bring the mixture to a boil for about 4 minutes, stirring constantly.
Pour the jam into prepared jars and seal well. Let cool before serving.