Thanks for the link...I'll be perusing through that later tonight. Good idea with the oil cooler valving or restricting for winter use. Control of ambient and environmental heat where you can will fine tune overall operational efficiencies. Basically the best is to raise adiabatic efficiencies. A book you absolutely have to at least flip through is called "The Romance of Engine" so here's a link:
The Romance of Engines - Takashi Suzuki - Google Books
Hino trucks had made some amazing breakthrough in diesel technology while Takashi was there. I guarantee you will learn some interesting ideas to implement. You've done a bunch of great improvements already. Again thanks for the link.