I found my pad heater did almost nothing mounted on the bottom of the pan because of the ribs, I moved it to the side of the lowest part of the sump (if that makes sense) and it seems to work better. This is the first year I’m not using my 80 as a winter daily and I can’t say I’m missing it, except for the snowstorm days.i’m not knocking it as i have an oil pan heater too. i just know that when i only use an oil pan heater my truck swears at me in -30C. when i have the webasto and no oil pan heater it fires right up and runs like when i start it in summer. it’s really not a competition.
now the kind of heater that goes in a bung in the oil pan may work better but mine doesn’t seem to create enough heat to make an appreciable difference. i use 15w40 all year too so it’s pretty thick at that temp