A process for reducing the rate of increase in pressure drop across a furnace convection section, the furnace convection section having a temperature profile. The process includes the steps of establishing a ratio of total dilution H.sub.2O to feedstock for the system, injecting a first portion of the total dilution H.sub.2O in the form of water into the convection section of the furnace, injecting a second portion of the dilution H.sub.2O in the form of steam into the convection section of the furnace, wherein a ratio of dilution H.sub.2O in the form of water to dilution H.sub.2O in the form of steam is established and varying the temperature profile across the convection section of the furnace by adjusting periodically the ratio of dilution H.sub.2O in the form of water to dilution H.sub.2O in the form of steam. A similar technique is conducted during decoking to remove asphaltene coke starting from the lower convection section upward. This upward decoking is accomplished by initially using more H.sub.2O in the form of water, then as the decoke proceeds reducing H.sub.2O in the form of water while increasing H.sub.2O in the form of steam.