Oil cooler for cooling lubricant oil in an internal combustion engine that has a cooling element that is arranged in the sump of the engine and has an essentially rectangular plate with longitudinal coolant channels over the major portion of its extent. The operator unit comprises a motor, an output drive assembly, a timing assembly unit, and a clutch assembly for providing selective engagement between motor powered operation and manual operation. A resonant section receives the signals from the input section in order to generate a resonant signal. The slot antenna includes a Radio Frequency feed line that operatively connects the tuners to the antenna element.