Type II are gas-slurped uboots, you will be forced to sail 1/3 ahead(3 or 4 knots) surface...
If you do, you can with the II type all the way to AM53 and back to base.
I tried that, and i maded...
But personly i like the VII class better, for me it's not about the "more fuel", for me it's "more torpedoes" & "Deck-gun"...
So i always start with career in Wilhelms haven...
Even my first mission was from Wihelmshaven to Grid CF and back without refueling
Thats what i called "saving fuel" and when i was in Wilhelmshaven i have 25% fuel left..