Eye contact ranges with so many people. I actually avoid eye contact with people that I like because I feel like the second my eyes are on them, they can sense it, so no thank you.
With me, there was one guy in my class who used to always always stare at me. Hes a typical, confident lad and was able to initiate conversation with me whenever he wanted to. But at random times, I would just find him staring at me. He would stare until I stared back and tried to style it out by laughing or says something quite funny. My friends started to tell me that whenever we were walking past him and he was with his mates, he would stop what he was doing just to stare at me again. Or like one time on the bus he made a joke and all his friends were laughing and I was with my mates and he kept on making jokes until I turned around and laughed. I thought it was a coincidence but my friends were sure that he kept looking to see if I laughed. I never confronted him about it because it is such a weird topic to bring up. But I knew for sure that he did not like me, he just wanted my attention.
Guys are likely to be oblivious to eye signals if they do not notice you. But if you catch their attention (e.g by looking gr8) and then engage in eye signal, they are likely to notice.