The International Cessna^® 170 Association

Hey All

I am trying to find the preferred oil temp ranges for my 0-300. My Scott Oil Temp Gauge does not have the range marked and I can't see the info in the flight manual? What are the min and max temps that I should be looking for.

Thanks

Kevin

According to the O-300 "Users Manual" the minimum oil temp for takeoff is 75°F. The Type Certificate for the O-300 does not list a minimum temp but for maximum temp states:
Maximum oil inlet temperature limit is 240°F, when using Spec. MHS-24 oil SAE No. 50 above 40°F
ambient and SAE No. 30 or 10W30 below 40°F ambient.

Kevin, I quartered my oil gauge and placed a mark on the face of the instrument at the approximate 180 degree position - in flight application seems accurate enough to gauge temp trends, i.e., colder than normal or hotter than normal.

Bob

Thanks for the info guys.

Robert are you saying that 180 degrees seems to be your normal cruising temp? I was flying the other day and getting temps of 150-160 degrees F. The OAT was anywhere from -10 degrees Celcius at altitude (oil temp ~150 F) to -5 degrees C (160F). I do not have any winterization plates. Do these temps sound low?

Kevin

Kevin at those temperatures with no winterization plates I'm wondering how you got temperatures that high.

So yes I think your OK except that it's generally thought that achieving oil temperatures of 180 or higher is needed to boil of any condensation in the motor. So that is the minimum I usually shoot for using winterization plates of the aluminum or duct tape variety.

I don't know where the popular idea that 180 degrees is necessary to "boil" out water vapor. Firstly, water vapor is ... uh... already vapor, and cannot boil, and liquid water will not boil except at 210, so...
Perhaps it's believed that 180 oil temp or greater is necessary to prevent the condensation of water inside an operating engine, but I don't believe water vapor will condense while inside any engine that is operating at cruise power settings. Long period/low-power arrivals and long periods of idling may do it at any oil temperature, however. (It's the cooling engine that condenses the water, which then flows down cool engine-walls to the oil sump.) Just an opinion.

Thanks George - it is nice to know that 180 is not a magical number. I was duct taping my cowl and doing other extraordinary things to get the oil temp up to or around 180 during (what we call) Winter here in Northern Calif. Without all the crap I can cruise in normal Winter temps here at around 160. If I don't have to worry so much about the magic 180 temp it makes things much simpler.

I agree that 180 degrees farenheit will not "boil" off the condensed water in the crankcase sump, but it will certainly encourage evaporation to water vapor which will then be expelled out of the crankcase through the vent line with the blow by. The higher the temperature, the better for that action to take place.

Robert Eilers wrote:Thanks George - it is nice to know that 180 is not a magical number. I was duct taping my cowl and doing other extraordinary things to get the oil temp up to or around 180 during (what we call) Winter here in Northern Calif. Without all the crap I can cruise in normal Winter temps here at around 160. If I don't have to worry so much about the magic 180 temp it makes things much simpler.

160 degrees is quite capable of encouraging water to evaporate and go out the breather. (Remember that all engines have a natural exit of crankcase air to atmosphere. After the small amount of air gets by the rings to the crankcase it is pretty warm and if it is not allowed to cool it will carry it's water vapor overboard. Keep your engine warm as possible during descent and taxi-in. Let it stabilize for 2 - 3 minutes at 800-1200 rpm before shutting it down. (The stabilizing period can be incorporated into taxying to the ramp.)
Avoid long idling periods afterwards. (There's nothing wrong with running it at 1200 rpm for a short period to clear the plugs, then pulling the mixture while simultaneously pulling the throttle shut. A non-turboed engine will thank you.)