For the first few days I had this A4 Avant 2.0 FSI, people kept asking me what the 'FSI' stood for. Rather than show up my ignorance on the subject, I joked it was onomatopoeic for 'fizzy'. But many a true word is spoken in jest.

On further investigation with Audi, I find it means nothing, despite the fact it stands neatly for the engine's main technological tour de force, 'Fuel Stratified Injection'.

For this is the engine developed from technology under the bonnet of the all-conquering R8 Le Mans cars, and is basically a common rail petrol engine. And it is fantastic. It fizzes along, literally as well as figuratively.

After a couple of years of diesel having it all its own way in fleet, grabbing all the headlines and winning all the awards, finally petrol is punching back, with this unit and BMW's Valvetronic engine leading the way.

While it is not especially fast, as 2.0-litre normally aspirated engines go it is very impressive, with 150bhp (compared to the standard 2.0-litre's 130bhp) and a 0-62mph time of 9.9 seconds. When BMW's Valvetronic is the only motor that compares, you know you're working in the right areas. On test I managed around the 33mpg mark, which is pretty good.

And with 170g/km of CO2 – a huge 20g/km less than the standard 2.0-litre engine – it is diesel-bashing on the tax front, without all the clunking and splunking of a diesel motor. Instead, there is the firm burn of a petrol motor, with a slight whistle as the pressure mounts in the common rail injectors.

This is how it works. As with common rail diesels, it injects fuel at very high pressure directly into the cylinder, rather than into the intake manifold as on most petrol engines.

The engine has two modes – a more conventional burn for high power and an ultra- efficient 'stratified' mode for normal cruising speeds. Here, the fuel air mixture is injected accurately towards the spark plug – rather than throughout the rest of the cylinder as is traditional – resulting in a burn with less waste.

But because the burn is so lean in stratified mode – there is a higher than usual concentration of air in the cylinder – an excess of nitrous oxide (NOx) emissions is produced. Audi has solved this problem with a gas recirculation system, cutting NOx by up to 70% in stratified operation.

The catalytic converter contains a NOx storage system that stores it up until full, and then sends it back into the combustion chamber to be burnt off, converting it into harmless gases. Clever stuff indeed.

Other things done brilliantly well in this car are build quality, cool style and refinement to name a few. But ride quality does not seem to be one of them, and I have not been impressed with many Audi cars I have driven recently on that front.

Our test car came with sports suspension so was even stiffer and I discovered a whole new selection of ruts and bumps on my daily journey up and down the A1. On the positive side, body roll is well contained, and grip is impressive for a front wheel drive car. I could live with it.

However, the equipment list is meagre. Cassette player rather than CD and no rear electric windows hint at the sort of omissions to expect, but this car is so classy and its engine so clever it more than makes up for missing a few toys.

Three rivals to consider

P11D price

That the Audi has the most expensive P11D price matters less because it is in the lowest tax band of the cars here (16%) with its meagre emissions. To get a BMW in this price range, the smaller 1.8-litre engine has to be chosen, and equipment levels are as meagre as the A4. A driver wanting high spec should consider the Laguna, which comes packed to the rafters, while the Alfa has as much lifestyle cool as the Audi, and at least has electric windows all round as well.

Alfa Romeo: £20,260
Renault: £20,280
BMW: £20,480
Audi: £20,530

SMR costs

Just because it is a premium brand, do not expect premium brand servicing and maintenance costs for the A4. It pushes the fleet-friendly Renault hard for the cheapest pence per mile figure here. It is not unknown for early Lagunas to be a little cantankerous on the electronic front though, although this may well have improved, whereas Audis have an enviable record of reliability now. The BMW is far off the pace in this section.

Renault: 2.33ppm
Audi: 2.83ppm
Alfa Romeo: 3.29ppm
BMW: 4.08ppm

Fuel costs

The new 2.0-litre FSI engine in the A4 Avant proves less thirsty than the 1.8-litre engine in the 316i, which is impressive. Keep the A4 revving low in lean burn mode and the fuel consumption is excellent. Work it heavily, and expect 30mpg. The Renault Laguna is not far behind the German duo while the 156 Sportwagon lags a fair distance behind the others, and would end up costing a substantial £828 more in fuel than the Laguna over 60,000 miles.

Audi: 9.61ppm
BMW: 9.86ppm
Renault: 10.66ppm
Alfa Romeo: 12.04ppm

Depreciation costs

Due to high construction standards and conservative but well conceived design, Audi saloons and estates never seem to age. As a result, residual values are excellent, and the A4 Avant here is no different. The same could be said of the BMW, although with a 316i badge on the back it is less desirable at resale and loses out to the A4. Alfas lose value because of build quality perceptions, real or imagined, and the Laguna does worst as badge snobs turn up their noses.

Audi: 18.63ppm
BMW: 19.25ppm
Alfa Romeo: 21.62ppm
Renault: 23.32ppm

Wholelife costs

Never out of the top two in any category, the A4 Avant wins the wholelife costs battle without breaking into a sweat. A consumate performer in all disciplines. Despite the worst depreciation, the Laguna does very well and comes third. Fleets looking for value and lots of standard equipment should look no further, especially in high-spec Initale trim. Badge snobs might opt for the BMW, but the Audi trumps it at every turn, while the 156 is never in it: too high on fuel and depreciation costs.

Audi: 31.07ppm
BMW: 33.19ppm
Renault: 36.31ppm
Alfa Romeo: 36.95ppm

Emissions and BIK tax rates

Yet again the A4 proves top dog. The new FSI engine delivers more performance and lower emissions, and is in the lowest tax band of the cars here, and so has the cheapest tax bill. The BMW is also fairly close, just one percentage band higher. The Laguna emits 190g/km of CO2, putting it in the 20% tax band, four points higher than the Audi. Prohibitively high emissions of the Alfa again leave it out on a limb.

Audi: 170g/km/16%
BMW: 177g/km/17%
Renault: 190g/km/20%
Alfa Romeo: 212g/km/24%

Verdict

Bags of style alone cannot save the expensive-to-run 156 Sportwagon and it is the first to go. The BMW 316i Touring follows. It has the smallest engine and poor levels of equipment, and a driver who insists on a premium badge will find the Audi betters it in virtually all departments. The Laguna performed well and would be the choice for those wanting high spec. But the A4 Avant FSI is a wonderful car in almost every respect. Classy, well built, with a truly fantastic engine, it is cheap to run for fleets and driver. The winner by a mile.

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