I personally wouldn't use it. I've taken kaplan FL 1 and 2, and compared to the real MCAT, I would say Kaplan tests sections are different:
Physical- Kaplan is less concept based, and I found it had more calculations and weird numbers to work with etc. than the real thing. so if you use kaplan tests, you would find the real test calculations easier, but would be caught off guard by conceptual, "qualitative" type questions. I found the physical questions more like the berkley review physics and gen chem books , the physics book especially was just like the real thing to me. The general chem questions on the real thing felt very close to the AAMC gen chem questions, they had the same style.
Verbal- I think the kaplan passages are both shorter and ask more detail oriented questions than the real thing. Use AAMC passages. The real thing is more about inferences, main ideas, authors opinions. Very few questions that you can directly find the answer in the passage verbatim, which Kaplan has many of these.
Biological- as far as resources I've used, the biological section on the real thing was somewhat different than any resource I used. The few organic questions that did show up felt like the ones you see in the AAMC. Most of the passages were like the SDN favorite, the AAMC 11 ebola experimental passage. So when you take that practice exam, pay close attention to how that passage and its questions require the use of passage info. You will see that on test day. Also the discretes were incredibly random, specific questions, I really don't know what advice to give on those, except know your stuff. I felt like I was in a game of Biology themed Jeopardy or something. Kaplan is alright in that aspect, but it lacks the experimental type passages that you need to be comfortable with for test day.