Combining the theory that pursues the maximum recovery factor and maximum profitability is not always an easy task, especially in highly viscous oil reservoirs. In order to avoid channeling and minimize viscous fingering (neither easily reversible), in fields with an adverse mobility ratio, recommendation tends to low injection rates, but how low is low? Which is the equilibrium between ultimate recovery loss due to a high injection rate, and time of recovery that maximizes profitability? Are there other variables that interfere in the former equation? How could these be manipulated?The Manantiales Behr Field located 35 km in the NW direction from the city of Comodoro Rivadavia, on the northern flank of the San Jorge Gulf Basin (Figure 1), combines highly viscous oil reservoirs with considerable petrophysical heterogeneities and compartmented reservoirs.There are several waterflooding projects in the zone with different injection history and results. The WF Zone named 1 was initiated in 2010. This project (with estimated 200 cp viscosity oil) showed a petroleum loss in response to water injection. Injection rate was initially calculated following traditional theories (Mobility ratio <= 1). A re-engineering of the zone determined to radically reduce injection rate, achieving an increase in the oil production ¿Did viscous fingering was partially reversed? Was it convenient to start a waterflooding project in this zone in the first place?Moreover, Zone named III located at the NW and next to the former, has a undoubtedly successful waterflooding project, high Secondary to primary recovery ratio and highly profitable. It was injected initially at a high rate, but on the other side well spacement has been reduced from the original 300 m.to 150 m. by infill drilling. Is this replicable to other areas?With a shorter history, Zone II started with a high injection rate and it was rapidly adjusted based on Zone I experience. The oil increase has doubled the expected profile so far.What lessons can we learn from these? Which is the optimal injection rate? Should it be maintained without variation during the whole project life? If acquifers are present or there is no energy left in the reservoir, is it still convenient to apply secondary recovery? What is the best pattern design for each case?The aim of the present study is to expose the lessons learned and expose a methodology to implement a successful waterflooding in viscous oil.