I'm not a chemical engineer, but I'll wing it with a couple observations. I believe oil bottles are made of HDPE (#2 recycle symbol). If not, ignore all my comments.
I assume the basic question is whether the oil inside the bottle is still OK. I see 2 reasons it might not be:
1) The oil got so hot that the oil or additives themselves broke down.
2) The plastic bottle got hot enough to release some chemical that contaminated the oil.
HDPE is a thermoplastic material. In other words, it can be heated to a temperature that allows it to be shaped or molded without breaking down. This happens somewhere around 250F.
I would say the answer to concern 1 is that if the bottle shows no sign of melting, the oil didn't get any hotter than it would be inside a normally running engine. No harm. On concern 2, the plastic melts at a lower temperature than it breaks down. Therefore the bottle wasn't hot enough to contaminate the oil. No harn there either.
Depending on how the bottle was labeled, you may no longer be able to identify the oil, making use difficult.
If the bottle isn't identified as HDPE, all this is meaningless. If it is some other material, the characteristics of that material may confirm the came conclusions.