I got 28 out of 31 and then quit when the website kept locking up on me.
I noticed that a lot of the parts didn't even exist when I last worked on my cars (about 40 years ago).
I hear ya...I actually feel pretty good about getting 37/48. A lot of this stuff didn't exist when I was a maintenance officer for the worst year of my Army career. It was one of those jobs that had all of the responsibility, but no authority.
About a month into my tenure, my motor sergeant and I took a hard look at every vehicle in our unit, resulting in a 4 page deadline report. That didn't go over very well with battalion HQ, especially the new acronym I developed for vehicles with more than a few things wrong with them: MFB (Mother F-----'s Broke). It was 1978-1979, during the Carter Administration, when the funds for maintenance and training were scarce, and most of our equipment was aged.
That job hastened my decision to not see the Army as a career. lol