Gentlemen:

+1 on this, with B757-300 RB535E4B version in P3d v4.5.

Occurs on climbout with TAT well above freezing and eng a/i off, although engine anti-ice would have no effect on oil temps.  Engine anti-ice directs high pressure bleed air to the nacelle lip/inlet cowl; it does not heat the fan, hot section, or accessory section -- thus, it would not touch the oil system at any point. 

On a similar note, low ambient temp would be insufficient to drive oil temp down to 29*c on a running engine.  Engine oil temps were confirmed at above 50*c prior to application of takeoff power, iaw Engine Start Procedure vol III pg.33.

Symptom is per screenshot by OP.

Cheers,

Jason