According to Wolverine guidelines, the KM454 oil capacity is best heated with their 250W unit. But because of the irregular shape of the KM454 oil pan, the Model 16 wouldn't fit anywhere. So I opted for a pair of Model 9.1 instead. They're 1.5"x6" and put out 125W each. I put one on either side of the driveshaft tunnel, then spliced the two AC cords into a pigtail.
You don't need a timer, and you don't need a higher wattage Wolverine. That's why you purchase them according to your engine oil capacity. They have a thermocouple that brings the oil up to 125F, and keeps it there. Just plug it in when you anticipate using the tractor in the morning - and it will control itself overnight. With a properly sized and installed Wolverine on the oil pan, -30F temps would have me more concerned about making sure the radiator, battery, and fuel system don't freeze up.
The installation procedure I posted pretty much follows the Wolverine instructions. The heaters are self-adhesive, cured with oil pan heat. The silicon they include is for sealing the heater edges, so that dirt and moisture cannot work it's way between the heater and the pan.
From the standpoint of using less electricity, I'd have preferred 240v. But that would have meant running a new circuit out to the shed. I went the cheap route, and bought 110v versions instead.
//greg//
