@smd4 posted:We never heated any of our oil.
What brand/kind of valve oil do you use? Most of the big mainline locomotives, with high superheat temperatures (like 4449, 844, & 3985) have used a synthetic high temp valve oil, originally from Exxon, called Celestic 1500 (good for steam temps upwards of 1000 degrees F). It is REALLY thick!