Oil Temp Gauges

[Jaybird180]

Where in the oil stream are they (the probes) usually located? I'm asking this question due to the use of them to indicate that the engine is being operated in a safe zone.

Is it possible that the temp probe usually lags overall engine temperature because of placement?

 

[Bob Noel]

Not a direct answer to your question, but I understood that CHT and EGT were better, more immediate, measures of operating in a safe zone. By the time the oil temps redline, bad things have been happening for a bit of time. (yes, I acknowledge that there is more to an engine than the cylinders.)

 

[Norman]

There are options on both Lycoming and Continental engines so it's basically where the airframe manufacturer decides to put them.

 

[Dan Thomas]

Oil temperature is measured at the inlet to the system. That's after the pump and before the engine's distribution system. If there's an oil cooler, the oil temp is measured after it leaves the cooler. It can come out of the engine hotter than the "redline" temperature.

Check the TCDS for whatever engine to see that they specify the oil inlet.

Oil pressure is normally measured near the end of the system, right before the relief valve. That will be the point of lowest pressure.

 

[JohnAJohnson]

Where in the oil stream are they (the probes) usually located? I'm asking this question due to the use of them to indicate that the engine is being operated in a safe zone.

Is it possible that the temp probe usually lags overall engine temperature because of placement?

My Lycoming O-360 is on the back of the engine just before the oil filter and it usually runs 180-190f. Sump -> Pump > Suction Screen -> Vernatherm > Temperature Probe > Filter > Main Gallery > Bearings, etc.. Keep in mind that oil temperature usually goes up about 50 degrees as it passes through a main bearing, and it cools back down almost as quick. This is where you get water boil-off, not necessarily at the 180-190 degrees you see on the gauge. Also, keep in mind that if you run your temperature probe at the front of the engine, it will read differently (higher I think) than a probe at the rear.