It's interesting, a quick browse of the specs suggests the hybrid 1.4 TSI has a higher compression ratio than the 2.0 310 TSI, suggesting that would benefit more from the anti-knock effects of 98 RON over 95 RON more than the 310hp TSI. Not sure you get more joule energy value from the same millilitre of fuel if the RON is higher though, nor that the engine can eek more joules out of it? I dropped chemistry after A level so happy to be corrected!