I have tried different types of engine heaters, from the lower radiator hose heater, to a temporary magnetic heater. Honestly, the one that doesn't preform the best is the lower radiator hose heater. It does work, and is easy to install, but there are better options out there. Probably the best is the freeze plug heater. But even that will not warm the oil, so I found the magnetic style block heater works the best.
You can leave them on, but since they are magnetic, I just take it off after the tractor starts. When I shut it down, I simply stick it back on the oil pan. This heater warms the oil allowing the oil to flow better during cold startup. The coolant doesn't get too warmed, so my glow plugs actually do something. In my tractor, the ECU reads the coolant temp to determine how long the glow plugs should run. If the coolant is nice and warm, the glow plugs don't fire, and I attempt a cold start. Some have said to simply turn the key backwards, to override it, but that does not work in my tractor (maybe yours?)
In all, the main concerns for me while attempting to start the tractor in cold weather are: 1) To actually start. 2) Protect the engine and turbo. 3) shorten warm up times. By warming the oil, all three are accomplished.
