May oil candles be used during the liturgy? In my parish only wax candles are used.
The Bishops' Committee on the Liturgy Newsletter addressed this concern in the November 1984 issue. The following is an excerpt from that issue.
The General Instruction of the Roman Missal (GIRM) states the following with regard to the use of candles: "The candles, which are required at every liturgical service out of reverence and on account of the festiveness of the celebration (cf.no.117), are to be appropriately placed either on or around the altar in a way suited to the design of the altar and the sanctuary so that the whole may be well balanced and not interfere with the faithful's clear view of what takes place on the altar or what is placed on it" In an interpretation of the previous GIRM 269, the Congregation for Divine Worship stated the following in 1974: The GIRM prescribes candles for Mass as a sign of reverence and festiveness'. But is makes no further determination regarding the material of their composition, except in the case of the sanctuary lamp, the fuel for which must be oil or wax (see Holy Communion and Worship Outside Mass, Introduction, no. 11). The faculty that the conferences of bishops possess to choose suitable materials for sacred furnishings applies, therefore, to the candles for Mass. That faculty is that they are appropriate for sacred use. Candles intended only for liturgical use should be made of material that can provide a living flame without being smoky or noxious and that does not stain the altar cloths and coverings. Electrical bulbs are banned in the interest of safeguarding authenticity and the full symbolism of light" (Notitiae 10  80, no. 4; see Liturgy Documentary Series 2: General Instruction of the Roman Missal, 112-113).
Since the National Conference of Catholic Bishops has never employed the above-noted faculty to permit the use of materials other than wax in the production of candles, the use of such other material either in substitutes for or in imitations of candles is not permitted in the liturgy. Therefore, oil lamps may be used only "in the case of the sanctuary lamp," as indicated above. Candles made of wax are to be used in the celebration of the Mass and other liturgical rites. Furthermore, because of their very nature, imitations of candles should not be used in the liturgy as, for example, "permanent" paschal candles, etc. Nor should electrical bulbs be used in liturgical celebration. In the interests of authenticity and symbolism, it is likewise most unfitting that so-called vigil lights be used for devotional purposes.