The Centre is considering allowing BS-VI petrol automobiles to be retrofitted with CNG kits, which could save about 40% to 50% on fuel costs. The Ministry of Road Transport has issued a draft notification to establish emission and other standards for such retrofits. This will be allowed for cars with a GVW of up to 3.5 tonnes, according to the ministry, and this type approvals for vehicles refitted with CNG kits will be valid for three years.