For the oil of the steroids to have the same effect as synthol does and rip the fascia for growth to occur you would need a lot off cc's worth of oil. If you think you can cause this with 2-3 cc's in the biceps per week you are wrong, so the best thing to to do is pick a steroid that has very low mg per cc and that way you can get a lot of oil in the intended bodypart without bringing up the mg's per week to high. To answer your question; Biceps, triceps, shoulders and calves are all common area's for site injections.

Quads are my favorite to self inject for the fact i can see what i am doing. its not as bad as people make it out to be. if you follow the right protocol of aspirating and doing it right, then there should be no issues. delts are another good spot.

I think the major confusion with site specific growth injections have to do with the understanding of how the AAS mechanism work. This would include how the compound(s) sit in depot, are then carried to and are taken inside a specific cell. There is a process or chain of events that have to take place, before the compounds are even active.

Take a step back and think about all the site specific injections you already do to your glutes, quads and shoulders. Those specific muscles would dominate growth, over those areas you do not inject. But that is not the case.

Now to the question what cases the growth. This is my own personal opinion. It is caused by two processes.
1) The mechanical stretching of tight muscle and fascia by the oil.
2) The inflammation caused by the stretching and injection results in more blood flow to the area.

you can inject anywhere where there is large amount of tissue and you only rotate around injections sites to minimize tissue scarring (glutes, lats, traps, calves, thighs, and deltoids etc.) or even some people have been using sub-q stomach injections with slim pins (29g) to avoid tissue scarring. i have done delt, glute, and quad injections and glute injections to me seem to be the best because it produced so little pip. I sometimes get pip from quad injections and almost always get pip from deltoids. injecting it into a certain spot will not increase that certain part of the muscle or make a difference in the muscle. if you want something that can just give you size and no actual strength or muscle try synthol.

Gear will not cause site specific growth. If it does its only temp and typically from swelling from a crappy injection. The only thing I have ever seen cause site growth is SEO like Syntherol.