There are just two diesel engines available in the R-Class, both 3.0-litre V6 units paired with a seven-speed automatic transmission. The entry-level 300 CDI has just 187bhp, but still offers decent performance, whereas the 350 CDI has a good deal more urge, and goes about its work much more smoothly. That makes it the preferred option.
The R-Class is intended as a luxury cruiser, so the emphasis is very much on ride comfort. It glides over any surface with impeccable smoothness, and even larger bumps can barely be felt. It suffers from the same body roll that blights all MPVs, but body control is better than on most, and the standard four-wheel drive on the top 350 CDI gives the car impressive grip in corners.
Both engines operate with the minimum of fuss, and engine noise melts away almost completely at speed. The car's containment of wind- and road noise is equally as impressive, giving the R-Class a superbly refined all-round drive. That's just as well, considering the car's purpose as a luxury cruiser.
Prices start at just under £40,000, so as MPVs go, this is as pricey as it gets. Mercedes dealers aren't shy about cutting you a deal, though, so you're unlikely to pay full whack. Fuel costs and company car tax bills will be steep, and although resale values are reasonable, they can't match those of Merc's mainstream saloons.
The R-Class has all the quality you'd expect from a luxury Mercedes. It uses classy materials and the build quality is excellent. We've heard of very few problems with mechanical reliability, although there have been reports of occasional electrical problems.
With active head restraints and six standard airbags, two of which are full-length curtain airbags, the R Class should perform well in a crash. A full set of electronic driver aids, including the Pre-safe system to minimise injuries in a collision, also helps to keep you out of trouble. All cars have an alarm and immobiliser.
The R-Class isn't particularly tall, so the driving position isn't as high as in some MPVs, but you still get a good view of the road. Rear visibility isn't so great, however - the rear headrests create blind spots at the corners of the car when reversing. Both front seats have full electric adjustment, so making yourself comfortable is easy, while the dash layout is logical, too.
The R-Class comes in either short- or long wheelbase forms (the 300 and 350 CDI, respectively), both with seven seats. The long wheelbase version provides all the passenger space that a luxury car needs, but the room you get in the shorter version is disappointing. Boot space is tight with the rearmost seats in place, but better when they're folded away.
Only Grand Edition models are available, and they come with alloys, parking aids and automatic wipers. There are four electric windows, with electric quarter-lights in the rear, as well as climate control, metallic paint and (artificial) leather upholstery. The on-board systems include a stereo with an Aux-in socket, Bluetooth and DVD-based sat-nav, while among the options are air suspension, two-tone leather upholstery and upgrades to the entertainment system.