Site injections are not a myth, but the oil is not going to work. You need to use synthol to achieve a lasting effect. The individuals who do this, utilize daily protocols of injecting - injecting ever-increasing amounts of oil in different sections of their bicepts - for example lower outer head, lower innerhead, upper outer head, outer inner head. These injections have to be made deep to the bottom of the muscle belly, where they actually push the muscle outward.
Injecting steroids in sites does not cause localized growth, as I am sure you know.
I wouldn't recomend site injections, as for the obvious dangers of injecting dirty fluid, and of course the fact that a good portion of that crap eventually has to be filtered by your kidneys.
Not to mention of course that site enhanced bicepts look like sh!t as they always look flexed - even when your arm is straight.
My advice is if you are dead set in your ways, do a lot of research in this area before you proceed. Right now, doing what you are doing is not going to have any lasting effect on your bicepts, besides local soreness and some temporary inflamation.
But know the risks. - Are you willing to jeopardize your health just for a pair of freakishly disgusting biceps? Your call.