i would vote on draining because you have a warmer substance and more surface area.
it is 5W30 motor oil that goes in it for ambient air temps of 95 deg F and below or you can use 10w30 but can cause damage if the ambient air temp drops below 32deg F so your best bet would be 5w30 but im not sure if you should use a synthetic oil or a conventional oil
C=40deg.-32deg. C=8deg. divided by 1.8 C=4.4 or 4deg.celcius
q=(275)(11)(1.00) q=3,025 cal remember that the formula to find heat is: q=m(DT)Cp and remember that the specific heat of water is: 1.00 cal/(gxC) you just replace values hope this helps:)