Dilution chilling dewaxing by modification of tower temperature profile

In a process for dewaxing a waxy petroleum oil stock comprising introducing said waxy oil stock into an elongated chilling zone divided into a plurality of stages and passing said waxy oil from stage to stage of said zone while injecting cold dewaxing solvent into at least a portion of said stages and maintaining a high degree of agitation in a plurality of the solvent-containing stages so as to achieve substantially instantaneous mixing of said waxy oil and said solvent thereby cooling said solvent-waxy oil mixture as it progresses from stage to stage through said chilling zone and thereby precipitating at least a portion of said wax from said oil under conditions of said high degree of agitation, separating the precipitated wax from a solvent-oil mixture and recovering a petroleum oil stock of reduced wax content from said mixture, the improvement which comprises adjusting the rate of solvent addition to the solvent-containing stages so that the greatest temperature drop occurs in the first solvent-containing stage of the chilling zone in which wax precipitation occurs with the subsequent stage to stage temperature drops in the remaining stages into which cold dewaxing solvent is injected and in which wax precipitation occurs progressively decreasing as the waxy oil-solvent mixture progresses through said chilling zone.