JMP direct oil temperature meter / analog display The original oil filler cap needs to be replaced with the direct blade. Note that the probe is often wetted only with spun oil. For example, a measurement on an oil drain plug gives a different value. NOTE: Carefully compare the thread diameter, length and height of your oil dipstick with your replacement part! ATTENTION: The air bubble in the sight glass fixes the expansion of the damping oil when heated, no reason for complaint!