You would certainly smell the fuel in the oil when you open the cap if the FCOC had an internal leak. This may be a case of overfilling. On occasions if you dry motor the engine then fill the tank you could overfill the motor(normally reads 2 to 3 litres down). This is because the pressure pump puts it in, but the scavenge pumps are not turning fast enought to take it out of the bearing sumps and back to the tank.