I live in one of the most dreaded climates in the nation. Therefore, I try to plug in my Honda Accord EX as much as possible during the brutal winters up here. Does an engine block heater keep the coolant warm or the oil warm? I plug my car in if the temp is 20F or -25F. Am I wasting my time by plugging my car in so much? Am I greatly reducing wear or being too anal? Should I just use the block heater when the temp is brtually cold?