The rishis further state

 The rishis further state Sarshapam Gandhatailam Yattailam Pushpavasitam| Anya Dravyayutam Tailam Na Dushyati Kadacana

Meaning: Mustard oil, fragrant natural-oil and oils extracted from flowers and mixed with other natural substances are usable. Massaging with the seasamum or mustard oil (as per the season) is supposed to be the best.