A control system and method for adaptively controlling transmission ratio shifting in an electronically controlled transmission. A refueling event is detected. After the detected refueling event, fuel consumption is monitored for a predetermined period during which a change in composition of fuel to the engine reaches or approaches a steady state. During the period, the rate of adapting transmission shift controls is modified to respond quicker to the change in shift characteristics induced by differences in torque produced by the engine. Implementing this method can improve transmission shift quality while the quality of fuel reaching an engine is in transition.