High-index oils are critical to the performance of optical electrowetting devices, such as lenses, prisms, and retroreflectors. Herein, the preparation and electrowetting analysis of 1-chloronaphthalene are reported. When 1-chloronaphthalene is mixed with small amounts of an alkane, the following properties can be achieved: refractive index > 1.60, viscosity < 5 cP for rapid switching, operation at < 10 V. and +/-45 degrees of electrowetting modulation around the condition for a flat meniscus (90 degrees).