The present disclosure, in one implementation, is directed to a method of estimating composition of fuel in the fuel tank of a vehicle. A refuel event is detected. A determination is made whether a volume of fuel added to the fuel tank satisfies a first threshold. A fuel composition estimation is suspended if the refuel event satisfies the first threshold. A total volume of fuel is accumulated based on a plurality of refuel events satisfying the first threshold. A new fuel composition is estimated based on the accumulated total volume of fuel satisfying a second threshold.