Advice: Used cars - best buys

A Mercedes? Isn't the three-pointed star meant to be the gold standard of retaining value? Ordinarily, yes  but not when it comes to £142,000 super saloons. You see, for years, Mercedes sold the old-shape S-Class in S55 AMG guise. With 500bhp, it was perfectly fast enough, and a snip at 'just' £91,000.

Then along came the lunatic S65 AMG; 604bhp, all the outlandish wheels and other AMG kit you can throw at it, a monumental £51,000 on the list price  for what? 0.4sec trimmed off the 0-62mph time. Oh sure, it did feel stupidly fast, with 738lb-ft of torque-defying logic. But how fast, really, do you want your luxury limo to be?

That's why most still brought the S55 AMG, and why the used market has had to correct prices to suit; the S65 AMG retains just 28% after three years, compared to 35% for the S55 AMG. That's three-year depreciation of £102,000. It loses more than the S55 cost new! But if you can find one for Glass's predicted price of £40,000 in 18 month's time, you've quite some car.

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