A new Mercedes SL for ΂£56,340? No, it's not a cut-price internet deal with a car specially built to Zimbabwean specification, but a new Mercedes-Benz SL350. That's a handy ΂£11,450 saving on an SL500, for a car which looks pretty much identical apart from the alteration of one badge digit and the transposition of another. A good deal? Let's see.

The key difference, obviously, is that the badge change reveals the loss of two cylinders, 61bhp and 1242cc. Less obviously, we lose the air-suspended Automatic Body Control and the five-speed automatic transmission, replaced respectively with ordinary steel springs and a six-speed Sequentronic manual with steering-wheel buttons and no clutch pedal. Adding ABC and auto, at ΂£2450 and ΂£670 respectively, bumps the price up to ΂£59,460. Now our saving over the SL500 is down to ΂£8330. Still tempted? Depends why you want an SL, I guess.

Now, with 245bhp and 258lb ft on tap from its 3.7 litres, the SL350 is not undernourished. (So why isn't it an SL370? Too numerically untidy, think the Germans as they screw up a perfectly good naming system). There's a chance, too, that the lighter nose could lead to sharper, flickier handling, not that there's much wrong with the SL500 here. And the 350 is also less thirsty than the 500, averaging 24.6mpg instead of 22.2.

Big deal, you're saying. I sense you are not convinced. But let's consider the SL350 as a smoothie sports car in its own right, and move it out of big brother's shadow. This isn't so hard to do: as soon as you twist the strange plastic object that deputises for a key, you hear a sound such as no current-shape SL has emitted before. The V8 woofle has gone, replaced by a smooth six-cylinder hum overlaid with quite a tasty edge once you exercise the engine a little. I'm not a great fan of Mercedes' V6s normally, finding them short of both punch and high-revs refinement, but this one is dissolving both prejudices.

The springs are coping with some lumpy Mexican road surfaces quite well, too. (Why Mexico? All will be revealed in a future issue.) There's a major bounce'n'check over the topes, Mexico's primordial speed bumps which punctuate every village, but that's to be expected. Otherwise this is a well-mannered, quite smooth but not particularly incisive drive, rather closer to the old-SL experience than I remember the SL500 being. Perhaps I remember wrongly, seduced by the thrust of that lovely V8.

Thrust is not the first word that comes to mind with this V6, I'm thinking, as we head higher into ever-thinner air and initial optimism ebbs away. It's starting to struggle a little now, and I'm relying on the autobox to find the gear to make the best of things. There's no Sequentronic for us to try yet, more's the pity, so I can't pretend I'm in a cut-price, push-button SL55. The slushbox is shifting fussily and often, but tries to hang on to the higher ratio for too long before letting go with a snapped-elastic surge into the lower gear. The V8 doesn't do this. So far, the SL500's extra thousands are looking like money well spent.

Then, as is so often the case on a car launch, everything feels better the next day. Must be something to do with the jet lag. The engine is keener and progress is cleaner, mainly because I've decided to ignore the dog and bark myself. Using manual mode to get the right gear when I need it, not a lurched second later, I can keep the momentum up and the engine humming. Now the SL350 is flying along well; the only tricky part is remembering which way to move the side-to-side shift lever for an up- or downshift. Surely, this slice of illogicality must exist only because Mercedes can't handle the idea of paying a Tiptronic royalty to Porsche.

The V6, then, is proving barely slower than the V8 on real roads (we have a 500 SL with us for reference), but I'm having to work at it harder. The small pace deficit is as much down to the blunter, rollier chassis as the engine, I suspect - and to prove it I try another SL350, this time with optional ABC. The result? It's the road to Tuxtla that we happen to be on, but it might as well be to Damascus. Never was there a better vindication of active air suspension, surely the springing medium of the future.

Topes are despatched as though the road surface is sucked in and squeezed out again. The steering's incisiveness and the body's lack of roll are as remembered from the SL500, plus a bit of the hoped-for added flickability thanks to the lighter nose. Here is an SL at its handiest as well as its most supple; Sport mode doesn't destroy the ride, neither does Normal mode soggify the handling. Cakes are both possessed and eaten. But for just ΂£8330 more...

With ABC, the SL350 is a credible sports car; without it, the cheapest SL slips into the boulevardier role of its recent ancestors. So, if image matters more than ultimate pace and poise, a steel-sprung SL350 won't make you suffer too much for your saving. But if you're spending nearly ΂£60K on an SL350 with ABC and auto, I can't see much point in not squeezing funds a little harder and buying a full-fat SL500. You know you'd regret it if you didn't.