New Mazda MX-5 RF vs used Mercedes-Benz SLK

Lightness is good in a sports car. Mazda’s latest soft-top MX-5 ticks that box, weighing in at a featherweight one tonne. With a folding metal roof, the weight goes up by 45kg in the targa-style RF (Retractable Fastback) version, but Mazda has tweaked the chassis to conserve the soft-top’s lively driving manners.

In 2.0-litre Sport Nav guise, an RF will cost you £25,695. But for £21,000, which is nearly £16k below the new list price, you can put yourself into a current-generation 1.8-litre Mercedes SLK 200. We know, because we found a less than two years old AMG Sport model in Palladium Silver with just 3700 miles on the clock for exactly that sum at Mercedes-Benz of Portsmouth.

The SLK introduced folding hard-tops to the compact roadster market in 1996. The current model a more substantial car than the Mazda RF, carrying an extra 350kg, but it also has an additional 23bhp and 51lb ft of torque over the 158bhp MX-5 RF. That equation amounts to better performance and better economy for the Merc. It does the 0 to 62mph dash in 7.0sec (against 7.4sec for the Mazda) and returns 43.5mpg (against 40.9mpg).

The German car is posher on the inside too, with generous wodges of soft-touch and satinised metal surfaces blending nicely with leather seats and precision switchgear. Those seats are firm but holding, and a good range of vertical adjustment means tall drivers aren’t head-butting the roof.

To drop the SLK roof you must first deploy the boot divider. This cuts your carrying capacity from 335 litres to 225, but that’s still a lot more than the MX-5’s handbaggish 127 litres. The Mazda’s elegant up-and-under roof-drop routine takes 5 seconds less than the 20sec taken for the Mercedes’ more straightforward operation.

There’s a cost-saving feel about the Mazda’s cabin. That’s OK, as it fits the car’s stripped-for-action intention, but even so it’s hard to ignore the quality difference between the two cars. The RF’s seats are as supportive as the Merc’s, but the relative lack of vertical adjustment means some drivers will have to bury their heads into their shoulders a little to avoid making roof contact. There’s no reach adjustment on the steering wheel, and no glovebox. Plus it’s a stretch to the poorly-sited infotainment dials.

The Sport Nav Mazda claws back some ground over the SLK with its extra toys, which include rain/dusk/rear parking sensors, heated leather seats, and a quick-acting 7.0in touchscreen with sat-nav. The SLK’s 5.8in screen is slothful by comparison, and has no nav.

The MX-5’s engine sounds unexciting at low speeds, but once it’s picked up its skirts from 1500rpm and into the fun zone between 3000rpm and the 6500rpm red line it displays gratifyingly instant throttle response and good ‘thrunge’. The sound becomes louder and racier and the short-throw six-speed manual gearbox is simply one of the best in motoring.

Our car’s AMG Sport-standard sports exhaust starts off a bit droney, moves into a sort of gruff chuntering and then gets pretty loud as you press on. It’s not as characterful as the Mazda but there’s lag-free urge on tap at anything over 2000rpm before the rush tails off at 6000rpm.

There’s not much between the two in a straight race but the Merc is slightly hobbled by a dull-edged seven-speed torque converter transmission that has to think for a second or so before it responds to paddle commands. When the shifts do arrive, it’s to the welcome accompaniment of some aural drama from the exhaust in Sport and Manual driving mode upshifts.

We mentioned earlier that the RF chassis has been tweaked, in the form of a front strut brace and Bilstein dampers on the MX-5 RF Sport Nav. Our Merc too has had a chassis twiddle in the shape of stiffened, 10mm-lowered AMG Sport springs and dampers and thicker anti-roll bars. It didn’t have the Dynamic Handling Package of adaptive dampers and speed-sensitive steering, which means it had some low-speed jarring over ridges, but overall the DHP is not missed.

The Mazda, with a much shorter wheelbase than the Mercedes, rolls and bobs about on fast country roads. The heavier and longer SLK is more settled, despite its heavy steering. Thanks to strong grip and traction, the Merc tackles the twisties with surprising aplomb, but take the same bends in the RF and you’re immediately mining a more engaging seam of involvement and responsiveness. As noted, roll is evident, but once the RF has adopted the right posture in a corner, its lovely steering and limited-slip differential prime it up perfectly for a Tarmac-gnawing exit.

That’s an important victory, but it can't disguise the fact that the SLK is in a different league for refinement when the roof is up or down. The Mazda is loud with the roof up, and distrubingly so when it’s down. Over time, and not very much of it, that would become pretty wearing and probably leave you wishing you’d gone for the Merc’s greater sophistication.

Make no mistake, there aren’t many cars that can top the MX-5 for affordable thrills. We’d stick with the soft-top though, and save £2000 in the process. The second-hand SLK doesn’t have the Mazda’s rawness, which is a good or a bad thing depending on the sort of person you are, but it pulls off the twin-role thing rather more successfully than the RF.