Oil won't have a single freezing point, it will slowly turn to wax, slush, and eventually more solid. Synthetic oils often list their "pour point" as -50F, when they still aren't solid, but won't flow when the container is held at 90 degrees for five seconds.
To make this thread more worthwhile - consider this: pour point doesn't mean anything to an engine. There are two other low temperature tests used and combined, they determine the "W" rating of an oil. The first test predicts the "cold cranking" viscosity. With carbureted engines, cranking speed determined air velocity through the carburetor, which then delivered fuel and perhaps the engine would start. If cranking speed was too slow, even with the choke on, it wouldn't start. The second test predicts flow through an oil pump pickup tube. Like a milkshake, you want to **** up oil and not **** a hole through the oil. This second test is much, much more critical today, since a fuel injected engine will start at almost zero RPM. If it does, it will run, whether or not the pump ***** oil or air. In carbureted engines there was a "safeguard" since if it couldn't crank fast enough, it wasn't going to start, and therefore couldn't run and **** air. SAE test after test has shown that the pour point temperature does not correlate with good starting performance, and it is not part of the "W" rating. Yet almost every bottle of synthetic oil has the -50F pour point on the label... (marketing!)