Review on Zerostart 3400062 Silicone Pad Heater for Engine Oil, Transmission Fluid, Reservoirs, and Hydraulic Fluids - 1½" x 6", 120 Volts, 125 Watts by Nuntawat Bridges

I bought these direct from a Wolverine dealer a few years ago. All three warmed up normally to the touch. So my guess is that the oil was also heated as stated in their advertisement. One day I checked it was working and found it still felt hot - one of the three pads was cold, I checked it was plugged in and turned on - but still cold. Wolverine quickly fulfilled the warranty and sent me a replacement. So the moral of this story is that you have to "believe blindly" that the pillow is actually on and working when plugged in. I have no idea when the faulty pad failed. Poorly. I plugged it in for hours and assumed my engine was covered in warm oil after starting - NO. My point is that even though it's plugged in, and other than getting under the car and touching the block, there's no way to confirm that it actually heats your oil.