The Volvo S60 D5 has been on sale in the UK for less than a year, but already it has been significantly improved. The changes all relate to the twin-turbo diesel engine, which has been worked on with a view to reducing component weight and internal friction, and in the case of cars (such as the one tested here) with six-speed manual transmission rather than the automatic alternative there's also a start/stop system.Although they're invisible to a casual observer, these changes have a substantial effect. Maximum power is up by 10bhp to 212bhp, leading to modest improvements in the top speed and 0-62mph time, while the official combined fuel economy and CO2 emissions have reached 60.1mpg and 124g/km respectively.The slower single-turbo D3 can't beat either of the last two figures, and the D5's CO2 rating in particular - no less than 15g/km lower than that of the previous D5 - is unmatched by any other car of remotely similar power.There are a couple of things to note here. One is that Polestar, Volvo's motorsport partner, has created an upgrade for the D5 engine which will boost its power still further to 227bhp at a cost of £645. That will become available later in 2011 and may harm the official economy and CO2, though bearing in mind the slightly unworldly nature of the economy test it may equally not do.Point two is that the automatic D5 - which, as you'll remember from the opening paragraph, doesn't get stop/start - doesn't even come close to the manual's green figures. Its 47.9mpg fuel consumption and 154g/km CO2 emissions mean it will be very much more expensive to run.But it's the manual we're considering here. Now, you might wonder how a car the size of the S60 could possibly average 60.1mpg (its actual CO2 compared with its official one is irrelevant, since you're taxed on what the EU test says the car emits). I was a bit dubious about the economy myself, but for part of this one-hour test I reset the trip computer, and if it is to be believed the S60 managed just over 50mpg on an admittedly unchallenging A-road route.A 10mpg shortfall might seem unfortunate, to say the least, but I've had worse, and if as an S60 owner I could manage 50mpg on a regular basis (which would mean using the performance potential very sparingly) I think I'd be happy enough.I have a few objections about the S60, and you can find them in the launch report of the range as a whole and this road test of the D3. A further degree of alarm was caused by the particular version tested here, as follows: its list price is £29,245, but Volvo had loaded it with so many extra-cost options that it would cost you a monumental £40,055.Hot damn, I thought when I discovered this, that's not cheap for something roughly the same size as a Ford Mondeo. Of course, Volvo is a premium brand and Ford isn't (though it has come closer to being one in recent years), but even so £870 for a sunroof and £630 per seat for powered adjustment strike me as being a bit excessive.I'd also shy away from ordering the 18" Sleipner alloy wheels (£795) because the low-profile tyres that come with them do horrible things to the S60's ride quality. On the other hand, I can't help liking the fact that they're named after a mythological eight-legged horse. Engine 2400cc, 5 cylinders Power 212bhp Transmission 6-speed manual Fuel/CO2 60.1mpg / 124g/km Acceleration 0-62mph: 7.2 seconds Top speed 143mph Price £29,245 Details correct at publication date