endurance is how long your engine will run over time
range is how
far you will go at the current speed
as freiwillige pointed out you have to strike a balance between speed and efficiency. too slow and you dont cover much ground, too fast and you run out of fuel sooner
i have found that - if i want to go a LONG way on a tank of gas then right about 8 or 9 knots is perfect.
You can really stretch the fuel if you remain submerged all day long at ahead slow and then run surfaced all night long at 8-9 knots.
another problem we run into in SH3....
the map is a "Mercator projection"... ie it is a flat surface representation of a spherical world.
The SH3 world gets its information as to where land and ocean are from the map... so the world in SH3 itself is in fact completely flat too!!
the further you go from the equator north or south, the more distorted the map becomes, this is why Greenland on the SH3 map nearly dwarfs north America.
ideally, the game would use curved nautical charts... which - if you had a large enough wall you could tape all the nautical charts together end to end and they would form a massive circle of charts.
the end result, even though a real life U-boat would have no real problem leaving St. nazaire and heading to New York... the game has added a significant distance between the two locations by "flattening" the earth.... so GWX crew had to mod the ranges of the U-boats to compensate for this mathematical travisty.