Matt Kimberley, PA motoring writer, puts Volvo's S60 DRIVe eco model to the test.

Fuel economy can be an elusive thing, but Volvo's range of DRIVe cars, pronounced 'drive-ee', are designed to help you find a little bit more of it. The S60 mid-size saloon is one given the eco-treatment and now boasts compelling fuel economy figures – on paper at least.

The topic of fuel economy is a hot potato these days. Most people tend either to acknowledge their car isn't especially economical and to worry about how much they're spending as a result, or they own a car that's supposed to be economical and isn't. Either way, everyone has an opinion.

The S60 isn't a small car. In fact its boot and passenger area are quite big, so it comes as something of a pleasant surprise to read that it will average 65.7mpg, rising to the mid-70s on a steady cruise.

Unfortunately, the EU tests just don't translate to real-world conditions. I had the pleasure of the S60 DRIVe's company for a week and covered 1,200 miles in it. After 200 miles of motorway cruising at 60mph using the cruise control, the economy readout was 66mpg.

The thing is, I couldn't have been gentler with it and there was little or no traffic to spoil the fuel-sipping party. There wasn't much wind and I had the air-conditioning off. I left the optional heated leather seats alone, too, leaving as few electrical components operating as possible to minimise draw on the engine.

After much more motorway driving, an evening sitting in huge lines of traffic, and a mix of conditions that exercised the engine stop and start function, fuel economy was at 55mpg.

It's partly due to something that's being overlooked by car manufacturers as their hands are forced by European law. Smaller engines, like the turbocharged 1.6-litre diesel in the S60 DRIVe, naturally have to work harder at higher loads, like in motorway driving for example.

Its turbo isn't working hard at constant motorway speeds, leaving the engine's natural grunt to do the work, and in cases like this, the engine is trying harder than a larger-capacity one would have to, so fuel economy suffers. If my cruising had been no more than 50mph, it'd be a different story.

Given that its main purpose is increased economy, the DRIVe doesn't make a great case for itself. But the point that's really proven here is that more eco-friendly cars like this are sensitive to how they're used. Low speeds, lots of cruising and considered driving styles are the order of the day.

Effectively, the S60 DRIVe has been tuned to be driven in a very specific way and it's the driver's job to do that if they want maximum fuel economy. The grabby operation of the clutch and brakes is typical of the car's highly-strung nature.

Whether motorists in the real world will want to put quite so much thought into their trip to the shops is another matter, and the fuel economy issue clouds what is otherwise a good car. Really direct steering makes it agile and quick to turn into corners, while the suspension strikes a decent balance of body control and comfort.

There are one or two major oversights on it, though. The lack of any space to rest your clutch foot is a problem because the foot well starts to feel cramped. The dashboard lighting is poor as well, with two old-fashioned bulbs creating brighter and darker patches across the clocks.

Standard equipment is a bit sparse on the entry-level ES model, but the list of options is huge. The list price difference from any DRIVe model to the much gutsier D3 version in the same trim is less than �850, and the latter isn't much thirstier when driven the same way.

The seats are comfortable and there are a good mix of storage compartments to accommodate drinks, coins, a phone and more. The big boot is useful and overall it's a very good all-round car.

If fuel economy was no issue I'd be reasonably happy with it apart from the lacklustre engine, but the fact that the engine struggles to provide its primary function is a tough obstacle for the rest of the car to overcome.