I wouldn't recommend using the McGraw Hill exams to gauge how well you're doing on the MCAT, but the content review is good to look at. I used the two exams, and they were really different from the practice AAMCs, as well as from the actual MCAT I took on July 18. I believe its only good for getting your passage timing perfected, and maybe for some content review. Nevertheless, I too was not able to find a grading scale for the exams. Maybe because they don't have enough data on overall student performances to develop a curve to scale the exam?