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Message: <blockquote data-quote="Schwepps" data-source="post: 396909" data-attributes="member: 3592">Firstly, RON is not an indication of the power of a fuel. It is only a measure of the combustibility of a fuel. The higher the RON, the less combustible. A base fuel is dosed with antiknock agents at the point of loading into a road tanker. Ie, the base fuel in the tank farm is homogeneous, and only becomes RON92, 95 or 97 at the tanker pump. In some countries, mixing is even done only at the petrol station.How RON affects your car's power output: An engine is designed with an optimum spark timing point at a certain crank angle before top dead centre (BTDC) called the 'advance'. This allows the fuel to ignite and achieve full burn at a certain optimum crank angle after top dead centre (ATDC) At this optimum point, the piston is just starting its downstroke and the full burn gives a maximum push. If your anti-knock sensor hears knocking, it will retard the spark point, resulting in full burn occuring past the optimum ATDC point, resulting in a weaker push. If there's no knock, there is no timing retard, and so NO LOSS OF POWER, whether the fuel is 98, 97, 95 or 92. Mass market cars have no knock sensors, so it makes no difference to their engines whatever RON is used.Modern engines do not knock easily because of advances in cylinder and valve inlet design to eliminate hot spots and introduce swirl of the air-fuel mix. If anyone tells you his car knocks using 95, he's only telling you his engine is old-fashioned or poorly designed. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink    ;)" loading="lazy" data-shortname=";)" />Knock is caused by high compression and temperature. Turbocharged engines have a higher tendency to knock than normally-aspirated engines because forced induction INCREASES compression, and compressed air is at higher temperature. That's why some cars have intercoolers to reduce the air-fuel temperature. But again, in a sophisticated engine, even a turbocharged engine should not knock using 95. It should only happen with non-factory designed aftermarket slap-ons where the design parameters are not considered at all.Phew! <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile    :)" loading="lazy" data-shortname=":)" /></blockquote>

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