Hi Paul,

It seems that many lubrication failures come from something restricting lube from flowing in the circuit it is suppose to.  Given that, any reduction in flow would seem to indicate a problem.  Sensing the oil temperature is fine if the oil is overheating for some reason, but if the flow is too low it may be that the oil temperature is low, rather than too high.
I'm wondering if a differential temp sensor that measures temp upstream and downstream of a cooling volume (length of stainless pipe with some form of heat sink ) would make a workable "low flow" indicator.  If the oil temp drops more than is expected after passing thru the cooling volume, wouldn't it indicate that the flow velocity was low?
Adjustment would need to be made for the temp diff between the incoming oil and the heat sink temp, of course, but that is a well understood thermal system.
I'm just thinking about a "no moving parts, no obstruction, low cost" sensor that looks for  flow reduction rather than an indirect method like sensing oil pressure.
If the circuit board with the thermal sensor signal conditioners and microcomputer on board were available, the remaining part of the sensor should be cheap to home-brew.
Possibly even as an attachment to an existing oil return line running to the oil cooler.

I admit it, I'm an instrument geek.  As if you couldn't tell ;-)

Craig Taylor