In our training, we are taught the need for preheating the engine when outside temperatures drop below freezing. Given the attention paid to oil temperature on start up, and observing my flight instructors occasionally turn the prop over by hand to “limber up” the oil, I suspect that like many pilots I assumed preheat was mostly about oil viscosity. My education took a giant leap forward a year into ownership, when the explanation given for why my relatively youthful engine would suddenly start shedding metal in the filter, was probably too many cold starts. It seemed likely that several years of flying club operations at the hands of a variety of pilots had taken their toll. That’s when I began to appreciate how small the tolerances are on the many moving parts within the engine and how the variety of materials each contract to a different degree with the cold and expand at varying rates as the engine heats up. I also learned that the detrimental impact is cumulative. Now, whenever I turn the key to engage the starter, I wince, in sympathy with the engine experiencing its harshest moment of operation, no matter what the outside thermometer or oil temperature gage, reads.
To be fair, I had always done my best to be conscientious about pre-heating whatever airplane I was flying when the weather was cold. I had dutifully applied the hot air generated by a scary propane-fired apparatus that seemed one spark away from uncontrolled conflagration. The truth is, whatever our best intentions, it is hard to do this well. The heating effect is unavoidably uneven, the time required is far longer than our intuition would suggest, or our patience tolerate, and the risk to belts, hoses, and paint finishes is much greater than we might believe. Worst of all, the one measurement available to suggest an adequate preheat – oil temperature – might not reflect adequate pre-heat to the bearings and metal interfaces, creating a situation potentially worse than no pre-heat at all.
After smarting from the cost of an unexpected engine repair, an electric pre-heating system suddenly seemed like an indispensable bargain. I chose a Tanis kit that not only applies a heating pad to the oil sump but also one to the upper engine block, as well as a heating element in each cylinder. Much has been written about the wisdom of leaving a pre-heating system continuously operating through the winter, with the principal concern being the potential for accelerated corrosion within the cylinder. Doug Evink, the President/CEO at Tanis, indulged me in hours-long conversation and shared company test data to convince me that with adequate heating of the entire engine block, and specifically, each of the cylinders, localized condensation that would precipitate corrosion could be precluded. In short, the system could be plugged in and all worries about timers and adequate soak periods, forgotten. It wasn’t long after the installation that I came to the conclusion that the peace of mind and absence of pre-heat hassle was well worth the investment. As it turned out, pre-heat would just be the first lesson in what would prove to be an expansive course of instruction in thermal management.