In this Market Trends we take a look at four Autobahn stormers; the Mercedes-Benz 450SEL 6.9, BMW 8-Series, Audi RS6 and Mercedes-Benz S55 AMG…

Mercedes-Benz 450SEL 6.9 (1975–1981)

The most intimidating sight in a 230E’s rear view mirror would have been the wide nose of the then-new S Class, and little other than the prodigious 450SEL 6.9 would have dispensed with that peasant’s Mercedes-Benz more embarrassingly. Even if he’d tried, the big V8 limo would explode past the 230E, covering that critical 70-90mph range in half the time: a blistering 6.1 seconds. Even boastful Saab would later need their 2.3 Turbo to conquer that time. Yet this autobahn König is only just being recognised. While R129 SL values have climbed convincingly, the W116 series is lagging behind, and it’s the 6.9 that is of most surprising value.

Particularly considering the some of the lofty prices its predecessor’s big V8 models catch, this 140mph bahn-stormer is still obtainable rather cheaply. Project opportunities as low as £5000 are increasingly rare these days, with the usual range being between £10-30k. According to The Market, prices for the W116 have been steadily climbing over the past five years, with examples of the 286bhp 6.9 halo model commanding only a slight premium.

But with film fame from Ronin, and fast Mercedes-Benzes far more prominent in enthusiasts’ minds than ever, plus rose-tinted nostalgia for pre-oil crisis decadence can only mean that the 450SEL 6.9’s time is nigh for full classic icon status.

BMW 8-Series (1990–1999)

BMW’s 8-Series was long misunderstood, perceived as a flagship for the sake of itself. Too big, heavy, and less practical than the 7-Series which was available with the same engines for less money. However, over the last decade, they’ve been developing a cult following that’s been nurturing values. Relatively limited numbers, especially in the UK, have meant that they have begun to seriously outpace the contemporary Mercedes-Benz SEC in the used market, and top CSi models are pushing big numbers. This past November’s Silverstone auction at the NEC saw one of only 138 UK supplied CSi models sell for £85,500.

Thankfully, you don’t have to spend quite that much to get behind the wheel of BMW’s 90s super-coupe. But prices are climbing, with even base 840Ci cars finding an extra thousand for each year or two that passes, with a further premium for desirable M-Sport package equipped cars. With £10,000 in your hand you’ll have a good choice of these V8 cars – the most common, while only 5 years ago this budget could have bagged you the higher-up, V12 850i. As E32 7-Series values creep up, so do those for this pillarless coupe whose impracticalities are less important to the classic buyer. Particularly good examples can now regularly be seen to breach £20,000, and even leggy CSi cars are tipping over the £50,000 mark. Don’t even mention the Alpina models. Sorry, that ship has sailed.

All models can blast down the outside lane at the expected 155mph with impeccable stability. A technical tour-de-force for BMW, the 8-Series showcased dynamic stability control, a low drag coefficient of 0.29, and adaptive dampers under its sleek, pillarless bodyshell. Numbers registered on the road are less than half of their 2001 presence, and now is the time to buy. In the meantime, if you see those slender pop-up lights trajected towards your place on the autobahn, we advise getting out the way – it could be a delimited 186mph CSi.

Audi RS6 (2002–2004)

In the same way that the Porsche 911 turbo and Nissan Skyline lit up the expressways of Japan, turbocharging changed the autobahn forever. One of the most brutal of this new breed was Audi’s RS6. The C5 generation cars are just about old enough now to be in their final market dip, so these 450bhp twin-turbo V8 Quattro weapons are currently performance bargains. The low end of the market carries examples at a paltry £7000, while sub-100,000 mile examples barely command above £10,000, and only the very best knock on the door of £15,000. This is especially remarkable since the production period was a narrow two years from 2002 to 2004, in which only 8000 units were built worldwide.

Rarer still is the saloon version, barely seen in generations since. Much of today’s Audi is indebted to the C5 RS6, which really hit its German rivals hard, especially on the autobahn. Its combination of Quattro stability, turbocharged thrust, braking (you can thank the outrageous eight-piston Brembo calipers for that), was a special recipe for Audi that continues today. Prices will soon begin to reflect this, as they already have for its kid brother, the B5 S4. Our advice? Pick up one that’s been cared for – maintenance bills can quickly overwhelm purchase prices – and show your fellow motorists the badge and exhausts.

 Mercedes-Benz S55 AMG (1999 – 2005)

Further along the high-performance Mercedes-Benz limousine saga, here in AMG flavour, is the W220 S55. Particularly in supercharged, 493bhp form, it makes for a compelling high-speed cruiser. Not only is there a vast quantity of torque, in the amount of 700nm, and a top speed pushing towards 200mph (if derestricted), but air suspension and adaptive cruise control add a calm to the proceedings that’s somewhat incongruous with its savage acceleration. There’s a reason AMG S-classes are still one of the most popular choices for German businessmen.

And yet the W220 versions are so cheap. Despite a distinct rarity, at least according to the DVLA where fewer than 200 examples are recorded online, they linger for sale between £8000 and a staggering £3500. There are good reasons for their impending appreciation, more than just dwindling numbers. This was the first AMG S Class available in UK RHD spec’, and this year marks the 20-year anniversary of the W220. You can expect the magazines to pour over the significance of Mercedes-Benz’s turn-of-the-millennium S Class very soon, and enthusiasts to then wake up to what they can buy for the price of a 300E. With W126 and W140 prices still on the rise, the W220’s value potential for now is in the desirable, iconic specs, and the best condition examples. Like the 450SEL 6.9, there’s only one way now for the genre defining S55 AMG.