Why is there no minimum "red line" limit for oil temperature in a Cessna 150?

Question

The POH states that the normal range is 100-240 degrees F, that the max is 240 F, but no minimum is noted.

Contrasted with the oil pressure green arc which is 30-60 psi, a max of 100 psi, and a min of 10 psi.

Thanks kindly.

Answer 1

Tempurature can't be too low. Not a good idea to takeoff until it's in the low normal range because oil pressure might exceed maximum but not necessarily. So there is no problem starting up on a cold day and taxiing out while the oil warms up. If it's real, real cold, you sometimes have to preheat the oil or the starter won't have enough power to turn over the engine. But if you can start it, no worries.

Answer 2

Starting an engine with congealed oil is always a risk even though there are oil by-pass valves and the like congealed oil is hard to move through all the oil passages that it needs to flow to properly lubricate the engine components and bearing surfaces. Things like oil lines, seals and oil coolers see pressure spikes that may be higher than the engineered rating of these components when they were new. Oil is not only the engines lubricant it is a coolant as well. Temperature and pressure are important things to watch closely and act on appropriately if you want your engine to last and give you top performance. You will note in your POH that you should have oil pressure within a specific time frame or you should abort the start. In light aircraft you can help this along by pulling the prop through a few turns prior to your start attempt.

Answer 3

I just happen to have a CE-150-M POH section 2-4 is power plant limitations. This gauge has no RED line, but it does have temperature limitations 116C (240F) this is the MAX limitation by the Teledyne Continental for the 0-200-A. It also states GREEN ARC Normal operating 100-240F. Anything over 240 is a considered RED line even if the gauge is not marked with RED.

You sould ask your A&P mechanic to look in the Cessna maintenance manual and see what the gauge marking should be. In some cases the green and red marking come off and have to be re-drawn. Check with your mechanic and their maintenance manual.

This gauge is a required instrument as described in the Code of Federal Regulations part 23.

§ 23.1305 Powerplant instruments.
The following are required powerplant instruments:
(a) For all airplanes.
(1) A fuel quantity indicator for each fuel tank, installed in accordance with §23.1337(b).
(2) An oil pressure indicator for each engine.
(3) An oil temperature indicator for each engine.
(4) An oil quantity measuring device for each oil tank which meets the requirements of §23.1337(d).
(5) A fire warning means for those airplanes required to comply with §23.1203.

Under the certification rules it explains how instrument should be marked.

Answer 4

There is no such thing as a "red line Minimum". Red lines always denote the maximum. Proper engine management dictates that you allow the engine to warm up a bit before maxmum throttle is applied. Most of the time the temp will be good enough by the time you get to the runway.

Answer 5

it would be pretty hard to have a minimum since the ambient temp is different at every airport in the world at any given time, the ambient temp will dictate the oil temp when the engine is not operating,