I track actual investments nearly religiously - and by actual investments I mean equity markets, real estate, bond market, etc. But, despite being a "market" of its own, I've never gotten into tracking car markets. Perhaps it's simply because they're just not attractive investments. MOST will depreciate, but even those that do appreciate, they fail to even keep pace with the S&P. So, even collector quality cars aren't good investments... they just happen to let you own something that you enjoy without completely losing your shirt on it. But, even then, there's opportunity cost.
I said this years ago when I bought my R8 - I mentally wrote it off as $0 from day 1. Of course it has value, but I'm never going to track it. First, because I don't intend to sell it. But second, because it would be depressing. At the purchase price of $191k (what I roughly paid with taxes), I calculated that the same money simply left in an S&P 500 index would be worth about $2.5M by "normal retirement age" in my case. That's real opportunity cost. The R8 could double or triple in value - which would be amazing AND unlikely - but it still wouldn't hold a candle to what I would have lost simply by failing to invest that money.
So, in my case, I look at as "entertainment." After all, that's what the R8 is for me. It's not a daily driver, I don't need it, and it serves NO purpose other than to entertain. From THAT perspective, I can argue it's a great investment... it's provided numerous smile-filled experiences... but it's an investment in quality of life, not a quantifiable financial outcome. For actual financial investments, stick to equities, real estate, businesses, and other proven wealth building instruments!