40 degrees ambient temp. Concern is that the oil will be a tad thick and not lubricate properly. As for internal temps, it is at ambient when I start, so as Eaglebeak said, tolerences are important and so is the viscosity of the oil. I think I'll just wait till it warms into the 50's before I crank it up. The compressor lives in an unheated shed, so I need to be careful.
Thanks for the responses, just wasn't sure and thought I'd ask the knowledge base we have for advice. I either find a way to warm it up, or I wait till Mother Nature does it for me.