Oil temperature question

[Captain Avgas]

Originally Posted by gmcjetpilot

Lycoming says 185F is min OT for normal Ops.

Sorry George, but I'm with Dan on this one.... you almost certainly just made up that 185F minimum. Show me where you got it from.

My Lycoming IO-360 Operators Manual states quite clearly that the "desired" oil operating temperature for continuous operations is 180F. That's not a minimum value either...it's the ideal medium temperature. Incidentally Lycoming don't provide a minimum temperature for take-off but Superior call for 75F.

The Sky Ranch Engineering Manual states that for the IO-360 the "desired oil temperature should be within the range of 160F to 245F with 180F being a medium value. Oil temps should not be below 165F during continuous operation."

So there you have it...180F is the figure to aim for...it's Lycoming's ideal temperature. And it makes sense because that temperature will be recorded at the oil filter adaptor and the actual temperature of the oil in the sump will be about 30F higher (ie about 210F).

The reality is that continuous operating temps in cruise of 180F plus or minus 15 degrees (ie. temps in the range of 165F to 195F) are ideal. Outside of that range pilots probably need to take a further look at their set-up.

We can't have pilots fretting unnecessarily that their oil temps aren't always over 185F in continuous operations.

[gereed75]

On a related note.....has anyone ever noticed change in engine noise associated with oil temp?

I perceive an audible low frequency rumble at lower oil temps, maybe below 140 or so. Sort of a background gear train harmonic on takeoffs and climbs on very cold days. It goes away as temps rise. Not sure if it corresponds in anyway with the opening of the thermostat, but maybe.

Might be a throwback to my days of driving Navy helos, when your ears were always tuned into a variety of gear whines, vibrations and harmonics.

[RVDan]

Originally Posted by gereed75

On a related note.....has anyone ever noticed change in engine noise associated with oil temp?

I perceive an audible low frequency rumble at lower oil temps, maybe below 140 or so. Sort of a background gear train harmonic on takeoffs and climbs on very cold days. It goes away as temps rise. Not sure if it corresponds in anyway with the opening of the thermostat, but maybe.

Might be a throwback to my days of driving Navy helos, when your ears were always tuned into a variety of gear whines, vibrations and harmonics.

Yes, but then I also am an old helicopter person.