Looking to splurge on an emotional investment that will quadruple your money in 10 years? Forget watches, stamp collections or even fine art. Buy a classic car.

Not just any old banger will do, though. According to the annual Knight Frank Wealth Report released this week, a ''truly investment grade car'' bought in 2002 would have appreciated by up to 395 per cent over the past 10 years.

The 1957 Ferrari 250 Testa Rossa that holds the world record for a car sold at auction of more than $16 million.

That makes cars easily the best ''passion'' investment you can make, well and truly outperforming popular luxury items such as fine art (199 per cent), jewellery (140 per cent) and watches (76 per cent).

The most sought-after cars tend to be Ferraris, with a 1957 Ferrari 250 Testa Rossa holding the world record for an auction of $US16.39 million ($A16.02 million), although a 1936 Bugatti 57SC Atlantic is believed to have changed hands for between $US30 million and $US40 million in 2010. Classic Aston Martins, Mercedes-Benzes and some pre-war Bugattis, Alfa Romeos and Rolls-Royces can also fetch prices in the millions.