Audi claims its revised A6 line is the world’s first in the executive class to feature tax-beating EU4 emission laws-compliant diesel engines. The range sold in the UK has more standard equipment plus standard automatic transmission for all six-cylinder petrol and TDI versions.

The two 2.5-litre V6 TDI engines – 163PS for front-wheel-drive models and 180PS for the quattros – have been heavily revised for full compliance with more stringent EU4 emissions regulations, which come into force in 2005. These engines also appear in A4 saloon, avant (wagon) and cabriolet models, and along with the latest four-cylinder 1.9 TDI and 2.0 TDI engines powering the new A3 hatchback, ensure that Audi can claim the largest range of EU4 compliant models currently available in the UK.

The A6 EU4-compliant diesel models reduce running costs for UK business users by eliminating the current 3% diesel tax premium. Removing the premium from the A6 2.5 TDI multitronic, for example, will mean a reduction in taxation charges for business users of over £850 in tax year 2003/4. In turn, this can increase the tax saving available by choosing an A6 over another prestige rival to over £2,500.

The tough EU4 emissions regulations have been met thanks to the use of modified components to reduce friction in the valve gear and improve cooling, increases in compression ratio (now 17.8:1) and fuel pressure (up to 2,000 bar) and European on board diagnostics for continuous monitoring of the exhaust emissions.

The majority of saloon and Avant versions of the A6 2.5 TDI are now EU4 compliant, with the exception of the 2.5 TDI quattro (180PS) in tiptronic form.

2.5 TDI quattro models with the no cost option of six-speed manual transmission are, however, compliant and qualify for the tax reduction.

A new wheel designed specifically for use with run-flat tyre technology is now available as an option for all four and six-cylinder A6 quattro models. The design of the ‘PAX’ wheel, as it is known, allows the driver to continue for up to 125 miles at a maximum speed of 50mph even if a tyre is fully deflated.

To ensure that adequate warning is given of an impending flat tyre or gradual loss of pressure, the PAX system is offered in combination with an automatic in-car tyre pressure monitoring display for the driver.

The Michelin PAX system consists of a special wheel rim, a modified tyre design and the actual emergency-run element - a support ring that sits close to the middle of the rim and encloses it. This technology ensures that the tyre remains on the rim even if it is completely deflated.

The PAX wheel can be recognised by its seven-arm design. Its size designation differs from conventional wheels, with a metric designation ”440”, which is roughly equivalent to a size 17-inch wheel. The tyre designation is 215/650 R 440.

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