Originally Posted by mkoesel
It could also perhaps be talking about volumetric efficiency, i.e. less fuel per unit of displament (but still more overall).
I was looking for that 8% quote. All I found in the original press release is this: "Over and above specific output of 105 hp per litre, average fuel consumption in the EU test cycle of 12.4 litres/100 km (equal to 22.8 mpg Imp) offers a clear expression of the engineering skill so characteristic of the engine specialists at BMW M GmbH." I did not find it in the engine press release, either.