Lycoming Operating Temperatures

[N941WR]

There have been a lot of discussion regarding high CHT’s.

The following numbers come the Lycoming Operator’s Manual for both the (I)O-320 and 360 Parallel and Angle valve engines and the IO-390:
(I)O-320
(I)O-360
IO-390

CHT’s
GENERAL RULES:
"For maximum service life, cylinder head temperatures should be maintained below 435°F (224°C) during high performance cruise operation and below 400°F (205° C) for economy cruise powers.)

Elsewhere in the manual (section 3, at the bottom of each page.):
"For maximum service life of the engine maintain cylinder head temperature between 150°F and 400°F during continuous operation."

Parallel or Angel Valve (I)O-320 and 360: 500°F (260°C) max temp
IO-390: 475°F (246°C) max temp

Time timing advance can have a significant impact on CHT’s. This is a big deal and it continues to surprise me how a few degrees too much advance can significantly raise CHT's.

Oil Temperatures:
"Oil Temperature: The maximum permissible oil temperature is 245°F. (118°C.). For maximum engine life, maintain desired oil temperature is 180°F (82.22°C)."

I have never been able to find a minimum oil temperature; however, I did find this:
"(e) Engine is warm enough for take-off when the throttle can be opened without the engine faltering."

Originally Posted by RV8JD

From the (I)O-360 Lycoming Operator’s Manual, Page 3-11:

" * - Engine oil temperature should not be below 140°F (60°C) during continuous operation."

Originally Posted by RV8JD

The IO-390s have a 10°F lower Max Oil Temp than the -320s and the -360s do. From the IO-390 Lycoming Operator’s Manual:

"(f) Oil Temperature: The maximum permissible oil temperature is 235°F. (113°C.). For maximum engine life, maintain desired oil temperature is 180°F (82.22°C)."

Thanks Carl!
- Note, this is continuous operation, not takeoff, climb, or decent. According to the Lycoming rep I spoke to years ago, this is the minimum temperature at which water will boil off. (The temperature probe is up higher in the engine and doesn't record the max temperature elsewhere in the engine or oil sump.)

(If any of you can find a minimum oil temperature for an (I)O-320, let me know and I will update this.)

Based on the above, having your CHT's rise above 400°F in climb is not an issue, as long as they drop back down in cruise.

[RV8JD]

Originally Posted by N941WR

(If any of you can find a minimum oil temperature, let me know and I will update this.)

From the (I)O-360 Lycoming Operator’s Manual, Page 3-11:

" * - Engine oil temperature should not be below 140°F (60°C) during continuous operation."

Originally Posted by N941WR

"Oil Temperature: The maximum permissible oil temperature is 235°F. (113°C.). For maximum engine life, maintain desired oil temperature is 180°F (82.22°C)."

Note that for the (I)O-360, the Max Oil Temp is 245°F (118°C), per Page 3-11 of the (I)O-360 Lycoming Operator’s Manual.

[snopercod]

Climbing out of GMU two days ago on a 90F day, my #4 and #3 peaked at 415F. I increased my airspeed to 120 Kts and that helped. In cruise the CHTs were 360 (1&2) and 380 (3&4). Oil temp was 190F. O-290-D2.

[RVDan]

One of the parameters that control min oil temp on takeoff is oil pressure. If the oil is to cold, the pressure may go beyond max limits. Bad stuff can occur if that happens.

[RV8JD]

Bill,
The IO-390s have a 10°F lower Max Oil Temp than the -320s and the -360s do. From the IO-390 Lycoming Operator’s Manual:

"(f) Oil Temperature: The maximum permissible oil temperature is 235°F. (113°C.). For maximum engine life, maintain desired oil temperature is 180°F (82.22°C)."