Jeep Grand Cherokee

I'm at the back of a rollercoaster, watching the carriages ahead crest the highest point of the track, Hangman's Hill. In turn, each one drops off the top and disappears rapidly, almost vertically, downwards. But these are not rollercoaster carriages at all, they're Jeep Grand Cherokee Laredos plummeting to the ground.

Now it's my turn. I select first in the low ratio 'box, creep forward, breathe deep and the car careers off. Staying clear of the brakes to avoid skidding, I rely totally on the turbodiesel engine's braking to keep things in hand. There's a scream, but it's not me, it's the engine. Just as it sounds like it'll burst, the track levels out and I'm back in control. Earlier, in the four-litre petrol car, it'd been hairier, the higher gearing of the automatic and lower compression of the petrol motor meant the descent was much quicker.

The 2.5-litre Turbotronic engine isn't nearly as powerful as its petrol buddy, but there's so much torque (205lb ft at 1,800rpm to be exact) that off-road it will pull itself up hills at idle. Drive, unlike the four-litre, is part-time 4x4. In normal conditions it's rear-driven, but you can manually shift to high-ratio 4x4 or low-ratio 4x4 on the move. Also manual is the five-speed gearbox, but the change is long, slow and agricultural and there's no space next to the clutch for your left foot to rest. So, when it comes to on-road driving, the automatic petrol car is much more pleasant. It's a damn sight quicker and quieter, too. The diesel's power band is very narrow and, though it will get to 97mph at some stage, it complains loudly when worked hard.

On A and B roads it's frustrating as the Grand Cherokee's road manners are among the best. It handles well without too much body roll and gives you more confidence than a Discovery. On motorways the engine stays schtum thanks to seriously high gearing which means you've got little acceleration, but at least it's comfortable. Adding to your comfort is a long list of standard goodies including air con, electric windows, power steering, cruise control, twin airbags, alloys and alarm/central locking - all for £26,495.

The petrol Laredo costs exactly the same. Or at least it does until you start driving, when the diesel's fuel consumption advantage makes itself known. Where the four-litre gulps fuel at 13mpg in town and 18.2 on the combined cycle, the diesel manages a less terrifying 23mpg and 29.7mpg. I'd have the petrol version, but then I do have a company Overdrive card

Nik Berg