Abstract: A fuel additive system is disclosed which comprises a sensing device for determining the flow rate of fuel into the system and for generating a signal in dependence upon the fuel flow rate, a control system for conditioning the signal to produce a proportional speed of a variable speed motor, a metering pump driven by the motor for dispensing an additive into the fuel flow at a rate proportionate to the speed of the motor, and a valving device for controlling the rate of increase in the fuel flow rate to permit the control system and the metering pump to respond to the variations within an effective response time to substantially maintain a predetermined ratio between the fuel flow rate and the additive dispensing rate.