Indraprastha gas Ltd (IGL) on Saturday slashed prices of natural gas supplied to automobiles by about Rs 6 per kg and piped to households as kitchen fuel by Rs 5 per unit, marking the first reduction in two years and bringing the tariffs to their lowest in the country. From Sunday, CNG (compressed natural gas) in Delhi will cost Rs 73.59 per kg, a reduction of roughly 8% from Rs 79.56. PNG will Rs 48.59 per SCM (standard cubic meter), down 9% from Rs 53.59.