I4 diesel arrives with 2012 update. Restyle includes new headlamps and bumpers

I4 diesel arrives with 2012 update. Restyle includes new headlamps and bumpers

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We learned in the last week, courtesy of IHS Automotive, that four cylinder engines are now most popular in the US, powering 43% of light vehicles sold in the first six months of this year. Six years ago, V6s had that sort of share. Blame high fuel prices and federal bureaucrats' proposed 2016 corporate fuel economy edict. This side of the Atlantic, the new 2012 four-pot XF diesel has its origins, at least partly, with government pen-pushers, in our case at the European Union.

The reason is the current bureaucratic obsession - from tinpot local council to Europe-wide Big Brother - with CO2 emissions ignoring, some observers say, other more lethal emissions that are not regulated to the same degree. Buy a new car in the UK and you'll pay a first registration tax based on its CO2 output. Your annual 'road tax' is CO2-based, free at the bottom [sub-100g/km] levels, draconian at Range Rover heights. Have the temerity to drive a company car and you'll pay 'benefit in kind' tax based on a proportion of its purchase price that increases with CO2 emissions. If they're over 160g, the employer gets taxed, too. And, if automakers don't get fleet-wide CO2 output down to an average sub-130g/km by 2013, the EU man will be along to tax, er, fine them, as well. And some local councils here in the UK have tried charging CO2-related prices for residential street parking, ignoring the obvious fact that parked cars don't actually emit CO2. We hear that led to councillors being voted out en masse at the next election.

Hence the new XF2.2. Engine from the diesel JV between former JLR owner Ford and PSA group, a 2,179cc, 190PS, 450Nm motor not unrelated to that in the Ford Mondeo and Land Rover Freelander mounted north-south for its first time and hooked up to ZF's new eight-speed autobox, with stop-start, both Jaguar firsts, and no manual alternative. CO2? 149g. Starting price in the UK when deliveries start in September: GBP30,950 for the SE trim level offered only with the 2.2. The three-litre V6 turbodiesel, GBP3,000 more than the 2.2 at each trim level price point, develops 240PS and 500Nm and emits 169g of CO2. The 2.2's official EU fuel consumption is less than the V6's on the official EU test cycle but real-world testing by consumer magazines and websites so far suggest this is not always so in reality, often the effect of putting a smallish engine in a big car to comply with legislation. That said, pre-launch publicity did include Jaguar-supervised test drivers getting 816 miles on one 14-gallon (64-litres) tankful.

The new four cylinder engine is part of a number of 2012 model year XF range updates including restyled headlamps and tail lights, reshaped bumpers, some minor trim/equipment upgrades and additional model variants.

Jaguar says 77% of its XF buyers are 'retail' (private buyers), hence 23% go to fleets, and estimates about 43% will now opt for the 2.2-litre diesel versions with 29% picking the standard V6 diesel, 25% the more powerful 'S' variant, 1% the five-litre petrol V8 and 2% the XFR sports models.

By trim, the entry level V6 diesel 'Luxury' has so far been most popular (almost 30%) followed by Premium Luxury (28.3%). UK 2010 volume was 12,687 in a market tightly contested by the likes of Audi's A6 which offers several I4 diesel options and BMW's 5-series.

I'm not up with Audi product but recent experience of a BMW 520d Touring (wagon) suggested Jaguar has run it close on refinement and driving enjoyment. On pockmarked Warwickshire country roads, the faint grumble of a four-cylinder diesel was almost always heard but not intrusive and the new ZF automatic shifted smoothly and chose its ratios well. You get 'paddles' behind the wheel for manual shifting - and that's fun - but I reckon why have a dog and bark yourself?

The 'intelligent' start-stop is excellent, halting the engine only when justified and restarting instantly. That, Jaguar says, is because it has a tandem solenoid starter motor with secondary battery, bi-directional crank sensor and fuel rail pressure holding system. The 'intelligent' bit is a 'change of mind' system; release the brakes before the engine stops and the injection system is refuelled and returns quickly to idle speed which also brings CO2 emission reductions of 5%-7%.

Overall ride comfort was good though a little busy at low speeds but the car just went where it was pointed and was so agile its relative bulk wasn't a problem on narrow, leafy lanes.

In contrast, the V6, with revised engine mounts and soundproofing for '12, was smoother, quieter and much faster (with less road noise that may have been tyre related), in return for higher fuel consumption and that emissions tax penalty.

One consumer writer summed it up well: If the company's paying, you'd choose the I4; if it's your cheque and you can afford the extra, pick the V6.