Q. Is it correct to use a commercial wick that comes covered with a wax coating even if you use olive oil, since the mitzvah is done at the moment of kindling, and you are using then wax, not oil?
If you use a decorative jar for storing the olive oil but it has no covering, and it stays uncovered overnight, can you still use the oil?

A. Halacha does follow the opinion that the mitzva is done at the time of the kindling (Shulchan Aruch 673: 2.) Nitey Gavriel (Chanuka 18: 8 n. 16) recommends therefore to pour some oil on the wick before lighting it, since the fuel for the flame at the beginning, is the wax coating on the wick, and only later does the oil start to burn.. However many Poskim deem the above unnecessary since they consider the whole process as one single act of kindling. (Halichos Shlomo Moadim 2: p. 285: n. 15, Avnei Yoshfe 6:103:8, Horav Chaim Kanievesky Shlita quoted in Doleh U’mashke page 237, and the opinions of Harav Shlomo Zalman Aurbach zt”l and Harav Elyashiv zt”l (quoted ibid. n. 633,)
Horav Shlomo Miller’s Shlit’a opinion is similar.

The second question has been addressed already in this forum in question 682 qu0ted bellow.

Can you use oil for Chanuka lighting that was left uncovered overnight?

Horav Shlomo Miller’s Shlit’a opinion is that it is permitted for a number of reasons. Firstly Poskim disagree whether in our days we should discard certain liquids that were left uncovered or Mashkim Megulim. The main reason for their prohibition is the possibility of their contamination by poisonous snakes (Avoda Zara 30a, Chulin 9b) and since that rarely occurs in our populated cities, we are lenient (Shulchan Aruch Y.D. 116:1, Mishna Berura 160: 23.) However, some Poskim do remain stringent (Pri Chodosh and Pri Toar, quoted by Birkei Yosef and Aruch ha-Shulchan Y.D. 116:1.) It is important to know that when Mashkim Megulim are prohibited they are even when left uncovered and unsupervised for a short time, not only overnight.

Poskim also differ if prohibited or non-kosher oil can be used for Chanuka lights and many are lenient (Sdei Chemed – M. Chanuka 14, Kaf Hachaim 673: 11, Beis Shlomo O.H. 10: 108).
However the main reason that oil left uncovered is undoubtedly permitted is that there is no Mashkim Megulim issue on oil, since snakes don’t drink from it (Chulin 49b, Bais Yosef Y.D. 116, Yemei Chanuka p. 71)

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a