40 degrees refers to the “specific gravity” of the oil, which is a measure of its density. There’s a good chart here if you scroll down some:
http://www.gcmwenergy.com/crude-oil-basics/
It looks like the oil coming out of this well might be heavier than 40 degrees though.
The U.S. National Bureau of Standards established the Baumé scale (degrees Baumé) as the standard for measuring specific gravity, or density of liquids less dense than water. API gravity, is a measure of how heavy or light a petroleum liquid is compared to water.
Not density. Weight as compared to the heavier weight of water. Density is varied by temperature. Weight is not. We still do not know the temperature of the oil. If it is very low, then its weight would be a more accurate metric. Not its volume at an undefined temperature.
“It looks like the oil coming out of this well might be heavier than 40 degrees though.”
Where is your support for this, other than what it “looks like”?