A fuel content detection system is disclosed. The fuel content detection system may include an engine control module (ECM) to receive a measurement of a parameter. The parameter may correlate with an amount of a substance in a fuel that is being consumed in an engine. The ECM may determine an estimation of the parameter based on a model. The model may use a predetermined value associated with the amount of the substance, and the engine may be configured to consume a designated type of fuel that includes an amount of the substance that corresponds to the predetermined value. The ECM may determine, based on the estimation and the measurement not being within a threshold range, that the fuel is not the designated type of fuel and perform an action associated with the engine.