I would use it but only when i could monitor it, like a long pre-flight. You can get a long thermometer and put it in the oil pan through the fill/dipstick neck and just use it to warm the oil. Wouldn't ever leave it on unattended. And do be careful not to overheat the oil. Oil heated beyond its design temp can get thick and stay that way, especially multi viscosity oils.
Truth be told I was a little hesitant to turn it on unattended. And given the temps we drop to up here over the winter what I did with my old plane was have the Switcheon system turn the heat on 2 -3 hours prior to me getting to the airport.
So here’s what I did. I ordered a new Reif system. Seemed like the right thing to do.
I think you made the right call. That heating element looks like it could put out a heck of a lot of heat and like others have said it could cook your oil. Even auto engine block heaters don’t look like that, looks more like a heating element from an oven. Don’t think I would use it, your call but why take the risk?
I have been using the EZ-HEAT sump heaters for years (in upstate NY). Simple to install and thermostatically controlled. Even in the dead of winter, if I turn it on before I go to bed, my oil and CHT temps are around 85*F in the morning.