Fuel or Speed
 

I have always wondered what U-Boat Caption did during the war on the way back to base after a patrol.

a) Travel back to base as fast as they could, base on there able fuel to minmum the turn-a-round between patrols.

or...

b) Travel back at slower speeeds to safe fuel for the war.

Which was more important, saving fuel or a quicker turn-a-round?

Usually fuel.
You would almost always go at the most fuel efficient speed (~7knts) if you are not chasing something or running away from something. This is still the case, even if you have 80% fuel, but no torps. You Still go home at cruising speed.
A) Fuel is expensive.
B) The motors will have a longer life.

Exceptions where made in dangerous waters (Biscay post '42).

Yep fuel efficiency is the most important
Most boats returned home with no fuel but plenty of torpedos
Quite the opposite of SH3

I read somewhere that 9 kts was the most fuel efficient speed..Is it? Does this vary depending on the boat you have + equipment?

Good question Seth :yep:
Despite the number of times this topic has come up I'm not sure anyone has come up with a definitive answer :hmm:

I always set for two-thirds, which is around 9 knots in a VII and 7 knots in a II. I could be wrong but I'm a trusting innocent soul and I'm also lazy.

7knts is the only value I can find with historical references.

In SHIII on a VIIC with no engine modifications the ideal speed in perfect weather is about 7.5 - 8 knts.

I have not studied how this changes with different boats / engines / weather.

I'd say fuel. You can't get home without it. So unless you have a big jussy target/convoy to blow to kingdom come, you stay put at the optimal speed!

Though it varies some, when surfaced and you're batteries are back up to 100%, you can have the Navigator check your maximum range at current speed and you'll get a fairly good idea of what you're working with.