That is one realism item I always turn off.
To me there is simply no fun running on 2/3 speed across the pacific. Yawn.
I am getting pretty close to my 100% realism but I don't think I will ever get there due to my fuel bias.
I remember on career, I forgot to deselect realistic fuel. I left Pearl at my usual flank speed. Got half way to Midway and got the "fuel warning"
Oops, ole "lead foot" here barely got to midway on fumes.