A new type of flat plate solar collector was utilized for heating fuel oil. In a previous work, two identical flat plate collectors of the conventional fin tube configuration were investigated. One collector was filled with fuel oil, and the other was filled with water. It was found that the efficiency of the fuel oil collector was 25% less than that of the water collector. In this work, two collectors were tested. One was the same conventional water collector, and the other was a trickle collector whose working fluid was fuel oil. It was found that the efficiency of the fuel oil collector was 15-19% less than that of the water collector. Comparing the results of this work with those of the previous one, it was found that the efficiency of the fuel oil-trickle collector is 4-9% larger than that of a conventional one filled with fuel oil. It is concluded that a considerable portion of the efficiency lost formerly due to changing the working fluid from water to fuel oil in the conventional collector was almost regained by changing the collector type to be a trickle one.