Autocar India says: The octane number (RON) of gasoline represents the fuel’s ability to resist knocking. A higher octane is more resistant to uncontrolled combustion or detonation, which is a key characteristic demanded by high-compression engines. Most mass-market cars, typically using naturally aspirated engines, are calibrated to work reliably on the default petrol available in India – 91 octane. However, gasoline direct injection (GDI) engines, such as the VW Group’s 1.0 TSI, 1.5 TSI and 2.0 TSI, Hyundai’s 1.0-litre GDI, Tata Motors’ 1.2 GDI, and several luxury cars tend to benefit from a minimum of 95 RON fuel. The higher octane number offers better combustibility in these high-compression engines, which also get the requisite ECU programming. When subjected to gasoline upwards of 95 RON, these engines adapt the ignition timing to offer 3-5 percent better power and fuel efficiency compared to when functioning on 91 RON fuel.