Not sure about the OP diesel, but hills in mine should be gone up at 1750 rpm and full throttle in the highest gear that will get me closest to that, followed by an unobstructed glide on the backend of course
But that is where I make the most power for a given amount of fuel on my tdi. Start gliding prior to the peak so that you glide crawl over the top and reduce need for braking as appropriate.
from ecomodders very own wiki (which anyone can edit/contribute to)
Brake Specific Fuel Consumption (BSFC) Maps - EcoModder