| CPC F02P 5/152 (2013.01) [F02D 19/02 (2013.01); F02D 41/0027 (2013.01); F02M 21/02 (2013.01)] | 3 Claims |

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1. An engine control apparatus for an engine, the engine being an engine in which liquefied natural gas as a fuel is allowed to be used, the engine control apparatus comprising a processor,
wherein the processor is configured to:
acquire a plurality of ignition retard control amounts for avoiding knocking in the engine in a plurality of cylinders, respectively, the plurality of cylinders being included in the engine;
calculate, as an index value, an average value of two or more ignition retard control amounts in two or more cylinders, respectively, among the acquired plurality of ignition retard control amounts respectively in the plurality of cylinders, each of the two or more ignition retard control amounts being lower than one or more of the acquired plurality of ignition retard control amounts, respectively, in one or more of the plurality of cylinders, other than the two or more cylinders;
estimate, based on the index value indicating the acquired ignition retard control amount, a methane number of the liquefied natural gas; and
control the engine based on the methane number.
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