Hi all, I'm new to both SHIII and this forum

I just have a quick question regarding fuel on a patrol. I am having a lot of trouble managing my fuel, for example in the very first patrol by the time i get to my assigned grid i am at 50% fuel or less and usually dont have enough or only just enough to get back to port. I'm just wondering if you guys could share any tips regarding this. One other thing is that i'm not sure if I am supposed to use the diesel engines only for traveling to my assigned grid and only use electric and submerge when i am expecting there to be hostiles? I am very interested in ww2 history but i dont know a lot when it comes to submarines or u-boats. Any help would be greatly appretiated thanks