In my opinion, this is a very crazy and ridiculous idea because it is very risky if you sell a car just to buy more ETH, if you don't understand speculation about a good ETH selling price, I think this is a big problem because you will get a loss for this, but if you understand price speculation, this is the right way for you, compared to borrowing from a bank just to buy more ETH I think you are more than crazy and silly.