Okay so I will be going into college come fall as a mechanical engineering major. For my major I need a general Chemistry class that I could opt out of with my AP credits. However should I do this? I took AP Chem as a sophomore and remember enough that I could review my notes that I saved and understand the general concepts but not in depth on all the topics (especially organic). Should I retake Chemistry in college? How important for my major is it or can I opt out with of the class without a huge impact. I will be taking course in subjects like thermodynamics and other topics that I considered a mix between physics and chemistry if that matters. Thanks for any help in advance and I can provide more information if needed. 
As an ME, if you can skip Chemistry, by all means skip it. It’s physics and math that’s your foundation, not chemistry. Thermo for example is physics/math. One exception would be if you plan on pursuing something related to Bioengineering, Biomechanics or Biomolecular engineering. In which case, you likely would need to have a strong basic understanding of chemistry.
Even biomechanics is mostly physics (statics and dynamics).
The AP Chemistry exam is one of the most comprehensive ones of the bunch, along with Calculus. I believe MIT takes those two for credit, and rightfully so. Even if you were ChemE I would say it’s not a terrible idea to use a 5 to get out of having to take it again.
Check the courses that you will take for all of your degree requirements. If none of them have the general chemistry course that you can skip with your AP credit as a prerequisite, then use your AP credit to fulfill the requirement. This is actually fairly likely for a mechanical engineering major.
If there are courses which do rely on the general chemistry course as a prerequisite that you need to take, then review the syllabus of the general chemistry course and try the college’s old final exams for that course. Then you can decide whether you know the material well (use your AP credit), know it well but have a few gaps (use your AP credit, but self-study the gaps), or know it poorly (consider retaking). Note that if the later course that needs general chemistry as a prerequisite is not shown in the course plan until a third semester or later, you may be able to defer the chemistry decision until after you get to campus and have a chance to talk to other students about whether the later course needs much knowledge from the general chemistry course.
My son is just finishing his freshman year in ME and did just what you are proposing. He liked chemistry, but is very happy not having to waste the hours or tuition to repeat it. Good luck!
Even for ChemE, you really want to move on to Org Chem instead of retaking Gen Chem. Unlike Calc, I don’t see a reason for retaking Chem for ME.
I personally don’t think you need to retake anything, Calc and Physics included as long as you follow @ucbalumnus and @boneh3ad’s advice to get old exams and syllabi from your university to verify that you know the material they (not just your HS AP teacher) expect you should know. Again n=1, but my son tested out of Chem, Physics 1, Calc 1 and 2 and is doing just fine.
MIT does not accept AP chemistry credit to fulfill chemistry courses, but does have its own placement test to allow entering students with strong general chemistry knowledge to place out of the first chemistry course there:
http://web.mit.edu/firstyear/2019/subjects/incomingcredit/ap.html
My DD is registered to take AP Calc BC, AP Physics AP Government and AP English Comp. She wants to pursue engineering but disliked chemistry. Do you think not taking AP Chem would be a detriment?
@smokinact, she will likely have to take chemistry one way or another. The problem with AP is that the credit application varies from school to school. Some will accept it as a full lab and lecture replacement, some for half only, usually lecture, some not at all. To make matters worse, at some schools it varies based on the AP score. So, depending on where she ends up, she could take AP and still have to take it again in college. I don’t think not having it will compromise her admission potential. It’s a pretty small piece of the puzzle, especially given the fact that she’s taking other rigorous courses. Good luck!
Thanks for everyone’s advice! I am still considering what I will do and will probably wait to talk with my adviser more before making a decision. So far I think I will opt out as I only have one class with a Chem pre req and some engineers and students I have talked to from ucf say that not a lot of chem is used in the course. Again thanks for everyone advice.
Take your credit - you EARNED it!! If you will not be using more chemistry, there is little reason to repeat it. I say this as someone who took 19 chem classes!
If you really want to make sure that you understand the material, I’d recommend taking a higher level chemistry course, such as OChem or PChem. A good rule of thumb that I heard and agree with is that to understand a topic well enough to teach it, you have to be two levels (i.e. courses) further along in that topic.
I feel like having a strong basis in Chemistry is always good. I could be wrong, but I doubt the Chem class you took in high school covers anywhere near the amount of information covered in college chemistry. People in my college chemistry class said that we covered more material in 1 lecture than they did in weeks of high school chemistry.
With that being said, I would probably skip it just because that’s how I am lol. If you’re worried that you might need it later on down the road then take it, it’s only 1 semester.
@smokinact I didn’t take Chemistry, Physics, or any math past Algebra in High School and I currently have a 3.87 in Engineering. It really doesn’t matter what classes you take in High School, I mean sure having taken AP Chemistry in High School will help, but in the end if you work hard you will still get the grades you want