With its pretty peanut-shaped headlamps and sleek, soft curves the Mercedes S-class of 1998 was a radical departure from the heavy-set, granite-jawed previous model. Customers showed their approval with dealers initially quoting an 18-month waiting list.

Since then Mercedes-Benz has been careful to protect the car’s desirability, introducing a diesel derivative, revising specifications and quietly reducing prices on some models by as much as £11,000 to ensure that sales would not stall.

Four years on, and with a wide choice of used examples, what should you look for in a used S-class? First choice is the engine, and the biggest seller from new is the S320 CDI diesel. With 197bhp and genuine 30mpg-plus economy, it makes a powerful case, although this desirability keeps prices high.

The S280 and S320 petrol versions come with V6 engines that are smooth but lacking in power, so they can be frustrating when you need to overtake. Go larger and you have a pair of V8 engines — the S430 and S500. Mercedes-Benz sells very few of the smaller V8 so you’ll probably be looking at the 306bhp S500.

One drive of the S500 ensures you forget the car’s size: it reaches 62mph in just 6sec and only stops pulling when it hits the top speed of 155mph. The reluctance of many buyers to purchase cars with large, thirsty petrol engines means you can pick one up for the same money as the S320 CDI diesel.

Topping the S-class range is the 6 litre V12 S600. At a price just shy of £90,000 when new, only a handful find homes every month, and used prices can vary enormously.

Equipment and standard spec also vary significantly on all models and that is further complicated by Mercedes-Benz’s habit of removing equipment such as the electrically adjustable rear seat to coincide with reductions in the car’s price. In March 1999 the S500, for example, gained Nappa leather seats as standard, but in September that year they became a £1,200 option. Unscrupulous sellers may try to claim a car has lots of optional extras when in fact they were standard when new, so check the original sales invoice to confirm.

Essential equipment on all models is leather upholstery, metallic paint, electrically adjusted front seats, and on cars with larger engines, satellite navigation and voice command.

The S-class air suspension system was a revelation when launched, endowing the car with crisp handling and refined comfort. Despite their relative lack of power the V6 cars offer the sharpest handling, thanks to the relative lightness of their motors.

Early criticism of the car’s minor switchgear and build quality was more perceived than real, and a look at high-mileage used cars will prove how robust they are. The large, well-lit dials are among the nicest around, and after familiarisation the switchgear layout works well.

Interior space is good and you can specify a long-wheelbase version on many models. But as with all prestige cars, service history and condition are important as repairs and refurbishment can cost dear.

On the forecourt

VITAL STATISTICS

Model: Mercedes-Benz S500
Engine: V8, 4966cc
Power: 306bhp
Transmission: Five-speed automatic
Fuel: 23.7mpg (combined)
Acceleration: 0 to 62mph: 6sec
Top speed: 155mph

Keys: Check you have all the originals as replacements are expensive; new cars came with up to four keys.

Warranty: Three years on all new cars.

Colours affect value: Avoid non-metallic colours even if they appear to be really cheap.

Imports: High desirability led to many grey imports. Check with Mercedes-Benz to confirm the car's build date.

Kerbed alloys: Can cost hundreds to replace, but can be refurbished for about £70 a wheel by specialists.

Upholstery: Leather on driver's seat prone to wear and can look tired on high-mileage cars.

Service history: A full history is essential. Be wary of lost or replaced service books.

Electrics: Check that everything works as repairs can be expensive.

Options: Standard specifications often changed, so look at sales invoice to confirm what was standard and what was extra.

THE ONE TO BUY

Mercedes-Benz S500 2000 V-reg with 30,000 miles and full Mercedes-Benz service history. Pay £30,000 at a dealer or £28,000 privately.

OR FOR SIMILAR MONEY...

2002 52-reg BMW 740i
2002 52-reg Jaguar XJR
2002 52-reg Audi A8 4.2 quattro
2001 51-reg Range Rover 4.6 Vogue
2000 X-reg Lexus LS 4.3

VALUES: Mercedes-Benz S500

Long-wheelbase car worth about £750 more than standard car. Source: estimates based on confidential CAP black book prices. 'Trade' is what a dealer would pay to buy your car; 'retail' is what you would pay a dealer.