The oil temperature in my O-320 with its rear baffle mounted oil cooler has always been on the cool side, possibly caused in part by efficient baffling. Even on the hottest days at sustained cruise, the oil temperature remains around 160? as displayed on the VM-1000 engine monitor. Because of that, I made up three cover plates with a pattern of holes of various number and diameter. This one is currently fitted and at present am seeing 170? at sustained cruise.
The Lycoming engine operators manual indicates 180? is the ideal oil temperature and that is the target temperature I constantly seek. Still, Lycoming Service Instruction No.1094D says in part the following:
For maximum service life, maintain the following recommended limits for continuous cruise operation:
Oil Temperature- 165?F.-220?F.
Hardly tempermental, that bulletproof Lycoming engine sure gives us a lot of leeway to work with.