[Mike] lives in a temperate rainforest in Alaska (we figured from his website’s name) and uses a 570 gallon oil tank to ... the oil level and finally opted for an ultrasonic sensor.

ToughSonic TC-100 and TC-200 non-contact, ultrasonic sensors include general-purpose and chemical-resistant models suitable ...

Directly adjacent to the float track on the outside of the tank is a long PCB with a couple of long, sinuous traces. These connect to an LX3302A inductive sensor IC, which reads the position of ...