No, we're not talking about that oil. That oil in the oil pan is NECESSARY to lubricate the entire geardrive assembly; proper name is clutch drive assembly. We're only talking about the part that engages the large drum gear, located at the very top of the entire assembly, called a drive pawl. One is silver colored and the other is blue (check pawl). You still need the 90W oil in the pan. Sometimes 160W oil was used in the oil pan instead to quiet the drive pawl from dragging over the teeth when the stoker was located where the clicking was annoying upstairs. The newer models have a thin metal shield used for many years to prevent that annoyance, so 160W oil should not be needed.
The older stokers that used the square blue gearbox at the lower end of the connecting rod use 20W oil and it is filled so that the level can be seen in the small street elbow at the lower end of the box.
The newer gearboxes are cubic and of gray color and are lifetime lubricated. No oil change is necessary and no oil is added unless it leaks.
The geardrive is located at the upper end of the connecting rod and the gearbox or (gear reduction unit) is located at the bottom end of the connecting rod and directly connected to the motor shaft.