Which preposition goes better with the below statement?
1: In the past few years I have learnt a lot about super cars.
2: Over the past few years I have learnt a lot about super cars.
To expand on FumbleFingers' comment:
I don't think there is any official rule, but to me, "over the past..." has always implied a continuous process, while "in the past..." implies discrete (separate) events. So one would say "I learned to drive over the past three years," but "I took my drivers' test sometime in the past year."
Where it gets a bit tricky is that multiple discrete events can be described as one continuous trend - so you could say either "I had met him several times in the past year," or "I had met him several times over the past year." What sounds better in these cases is, as far as I can tell, quite random, so I unfortunately can't give a rule, but either is correct.
For the example you gave, you described a process (the process of learned about supercars), so I would use "over" in this case.
I don't think there is an 'official' way of saying this, but I would say that "over the past few years" sounds more natural to me, coming from England. It's your call really, since everyone will understand what you're saying regardless of which of these ways you say it.