The Audi A8 (D2) 2.5 TDI V6, produced between 1997 and 1998, represented a compelling entry point into Audi’s flagship luxury sedan range. Positioned within the D2 generation (also known as the 4D chassis code), this variant offered a diesel-powered alternative to the gasoline engines available, primarily aimed at European markets where diesel fuel was more prevalent and economically advantageous. It served as a more fuel-efficient and torque-rich option compared to the higher-specification petrol models, though it sacrificed some outright performance. This model occupied the lower-mid range of the A8 lineup, offering a balance between luxury and economy.
Technical Specifications
| Brand | Audi |
| Model | A8 |
| Generation | A8 (D2, 4D) |
| Type (Engine) | 2.5 TDI V6 (150 Hp) |
| Start of production | 1997 |
| End of production | 1998 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 10.3 l/100 km (22.8 US mpg, 27.4 UK mpg, 9.7 km/l) |
| Fuel consumption (extra urban) | 5.6 l/100 km (42 US mpg, 50.4 UK mpg, 17.9 km/l) |
| Fuel consumption (combined) | 7.3 l/100 km (32.2 US mpg, 38.7 UK mpg, 13.7 km/l) |
| CO2 emissions | 197 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 9.9 sec |
| Acceleration 0 – 62 mph | 9.9 sec |
| Acceleration 0 – 60 mph | 9.4 sec |
| Maximum speed | 220 km/h (136.7 mph) |
| Emission standard | Euro 2 |
| Weight-to-power ratio | 10.6 kg/Hp, 94 Hp/tonne |
| Weight-to-torque ratio | 5.1 kg/Nm, 194.4 Nm/tonne |
| Power | 150 Hp @ 4000 rpm |
| Power per litre | 60.1 Hp/l |
| Torque | 310 Nm @ 1500-3200 rpm (228.64 lb.-ft. @ 1500-3200 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | AFB |
| Engine displacement | 2496 cm3 (152.32 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | V-engine |
| Cylinder Bore | 78.3 mm (3.08 in.) |
| Piston Stroke | 86.4 mm (3.4 in.) |
| Compression ratio | 19.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 5.5 l (5.81 US qt | 4.84 UK qt) |
| Coolant | 8 l (8.45 US qt | 7.04 UK qt) |
| Kerb Weight | 1595 kg (3516.37 lbs.) |
| Max. weight | 2195 kg (4839.15 lbs.) |
| Max load | 600 kg (1322.77 lbs.) |
| Trunk (boot) space – minimum | 525 l (18.54 cu. ft.) |
| Fuel tank capacity | 90 l (23.78 US gal | 19.8 UK gal) |
| Max. roof load | 100 kg (220.46 lbs.) |
| Permitted trailer load with brakes (8%) | 1900 kg (4188.78 lbs.) |
| Permitted trailer load with brakes (12%) | 1700 kg (3747.86 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Permitted towbar download | 75 kg (165.35 lbs.) |
| Length | 5034 mm (198.19 in.) |
| Width | 1880 mm (74.02 in.) |
| Width including mirrors | 1973 mm (77.68 in.) |
| Height | 1440 mm (56.69 in.) |
| Wheelbase | 2882 mm (113.46 in.) |
| Front track | 1597 mm (62.87 in.) |
| Rear (Back) track | 1586 mm (62.44 in.) |
| Front overhang | 1018 mm (40.08 in.) |
| Rear overhang | 1136 mm (44.72 in.) |
| Drag coefficient (Cd) | 0.3 |
| Minimum turning circle (turning diameter) | 12.3 m (40.35 ft.) |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the front wheels of the vehicle. |
| Drive wheel | Front wheel drive |
| Number of gears and type of gearbox | 6 gears, manual transmission |
| Front suspension | Independent multi-link suspension |
| Rear suspension | Independent on trapezoidal lever |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 225/60 R16 |
| Wheel rims size | 7J x 16 |
Powertrain & Engine Architecture
The heart of the A8 2.5 TDI was the AFB engine code, a 2.5-liter V6 diesel engine. This engine utilized a direct injection system, a relatively advanced technology for the time, which improved fuel efficiency and reduced emissions. The engine featured a turbocharger with an intercooler, boosting power output to 150 horsepower and 310 Nm (228.64 lb-ft) of torque. The engine employed a double overhead camshaft (DOHC) valvetrain, contributing to its relatively smooth operation for a diesel. The engine was mounted longitudinally in the front of the vehicle. While a 5-speed manual transmission was available, the majority of these models were equipped with a 4-speed automatic transmission, designed to provide comfortable and effortless cruising. This automatic gearbox, while reliable, wasn’t known for its particularly quick shifts or sporty feel.
Driving Characteristics
The 2.5 TDI V6 automatic A8 offered a relaxed and refined driving experience. The abundance of torque, readily available from low engine speeds, made it a capable cruiser, particularly well-suited for long highway journeys. Acceleration was adequate, with a 0-60 mph time of around 9.4 seconds, but it was noticeably slower than the gasoline-powered A8 variants. The automatic transmission, while smooth, contributed to a less engaging driving experience compared to the manual option. The gear ratios were optimized for fuel economy and comfortable cruising rather than outright performance. The focus was on providing a quiet and comfortable ride, typical of the A8’s luxury positioning.
Equipment & Trim Levels
The A8 2.5 TDI typically came with a generous level of standard equipment, befitting its luxury status. This included features such as leather upholstery, power-adjustable front seats, automatic climate control, and an upgraded audio system. Optional extras included a sunroof, upgraded wheels, and a navigation system. The interior trim was generally conservative and elegant, reflecting Audi’s design philosophy of the time. The dashboard layout was clean and functional, with a focus on ease of use. The specific trim level could vary depending on the market, but generally, the 2.5 TDI occupied a mid-range position, offering a good balance of features and price.
Chassis & Braking
The A8 (D2) featured an independent suspension system on all four wheels, providing a comfortable and controlled ride. The front suspension utilized a multi-link design, while the rear employed a trapezoidal lever setup. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. An Anti-lock Braking System (ABS) was standard, enhancing safety and stability. The chassis was designed to provide a stable and secure platform, minimizing body roll and maximizing ride comfort. Stabilizer bars were fitted to both the front and rear axles to further reduce body roll during cornering.
Market Reception & Comparison
The A8 2.5 TDI was generally well-received by automotive critics, particularly for its fuel efficiency and comfortable ride. It was seen as a practical and sensible alternative to the more expensive and less economical gasoline-powered models. Compared to the higher-output A8 variants, such as the 4.2-liter V8, the 2.5 TDI offered significantly lower running costs but sacrificed performance. Against other diesel-powered luxury sedans of the time, such as the Mercedes-Benz S-Class diesel, the A8 2.5 TDI offered a competitive combination of performance, refinement, and price. Reliability was generally good, although diesel engines of this era could be susceptible to issues with the fuel injection system and turbocharger.
Legacy
The Audi A8 (D2) 2.5 TDI V6, while not the most powerful or prestigious variant of the D2 generation, remains a respected and sought-after classic car. The AFB engine, when properly maintained, proved to be a durable and reliable unit. Today, these cars are increasingly appreciated by enthusiasts for their understated elegance, comfortable ride, and relatively low running costs. Finding well-maintained examples can be challenging, as age and mileage take their toll. However, the A8 2.5 TDI continues to offer a unique and rewarding driving experience for those seeking a classic luxury sedan with a diesel heart.
