[oil pan 4]

Trying to control heat flow between 2 fluids, now you are getting into industrial controls.
Which is what I do at work and there is no real easy way to do it.
(this is why I advocate the use of very direct heating via tube in shell heat exchangers and immersion heating elements)
That reminds me I have been meaning to do a spiel about how a vehicle is just like a production process and how all you have to do to make a vehicle more efficient is set it up to resemble a plant production process a little bit more.