travel at 8 knots for long distance patrols this is the most fuel efficient speed:salute:

keep an engineer officer in the diesel room too

edit: yes, for the type VII, my apologies

I see ahead 1/3 is quite efficient, but takes forever!....:D

Fuel is blood :salute:

Different classes of boats will have different "most efficient" speeds. YMMV, never truer. Best thing is to assess the performance of your own boat. The "Report range at current speed" order lets you do that. Optimum cruise will usually be between 8 and 12 kts. Operational ranges for all boats of all nations were spec'ed and measured at 10 kts, so that's what the designers aimed for. On the outbound leg to your patrol area, try a few speeds. In clear safe water on a fair day, set TC 8 (to give your speed time to stabilize). Then just set each speed and quiz the Nav about range at that speed. IIRC, US military usage sets "Bingo" fuel - return to base - at range to base plus ten percent. You can get your range to base in various ways. But there's no need to guess or use rules of thumb, and no need to RTB with half a tank of gas, either.

This is pretty much how the R/L skippers did it. But, if you are eager to BSU and consider fuel management a dull bother, you can just uncheck "Limited Fuel" in the realism (sic) options menu and never have to worry about running out of fuel again.