Hilchos Chanukkah / leftover oil after Chanukkah (b) – 32

1. It is forbidden to save the oil left over in the Chanukkah lamps for use the following year, for fear that the person will forget that it is mitzvah-designated oil and will come to use it for private use (and Mishnah Berurah 677:19).

2. It is even forbidden to keep this oil in a repulsive container, despite the fact that in this case there is no likelihood the person will eat it, because there is nevertheless a fear that the person will use it for mundane light, which is also forbidden (ibid.).