We have thoroughly studied the Audi 4.2 BAR engine and in this article we will examine its specifications, problems, failures, service life and reliability. We will also look at operating features: which oil to use, how often to change it, and what fuel consumption to expect under real-world conditions.

Problems and Failures of the Audi 4.2 BAR Engine

The Audi 4.2 BAR is a 4.2-liter V8 engine used in various Audi models. While it is generally regarded as durable, there are several known issues that owners should be aware of. Below is a list of common problems, typical mileage when they appear, and estimated repair costs.

Common Issues

  • Timing chain wear (including guides and tensioners) - often occurs around 80,000-120,000 miles. Symptoms include rattling on cold start, especially from the front of the engine. Repair cost: $2,500-$4,500 depending on shop and parts.
  • Oil consumption due to valve stem seals or piston ring wear - typically appears after 100,000 miles. Symptoms include blue exhaust smoke on startup and increased oil usage. Repair cost: $1,500-$3,000 for seals, more if rings are replaced.
  • Camshaft adjuster issues (if equipped) - may cause rough idle or reduced performance. Often occurs around 60,000-90,000 miles. Repair cost: $800-$1,200.
  • Coolant leaks from plastic coolant pipes (especially in the valley) - can happen after 60,000 miles. Symptoms include coolant loss and overheating. Fix by replacing with metal pipes, cost: $500-$1,000.
  • Spark plug tube oil leaks - valve cover gaskets degrade, leading to oil in spark plug wells. Common after 70,000-100,000 miles. Replacement cost: $300-$600.
  • Ignition coil failures - fairly common, especially in high-mileage engines. Symptoms include misfires. Replacement cost: $200-$400 per coil (DIY).

Prevention: Regular maintenance is key. Use high-quality synthetic oil with the correct VW/Audi spec, change it more often than recommended (e.g., every 5,000-7,500 miles) to reduce sludge, and inspect timing chain condition by listening for rattles on cold start. Replacing coolant pipes proactively at higher mileage can prevent major overheating. Always address small oil leaks early to avoid damage.

Reliability and Service Life

Audi never officially stated a specific service life for the 4.2 BAR, but it is known as a robust engine. In real-world use, well-maintained examples can easily exceed 200,000 miles. However, neglect significantly shortens its life.

Well-maintained: With regular oil changes using correct VW 504 00/507 00 oil, timely coolant changes, and proactive timing chain service, many owners report 200,000-250,000 miles without major mechanical failure. Some long-distance drivers have reached 300,000 miles with regular care.

Neglected: Skipping oil changes, using wrong oil, ignoring coolant leaks, or avoiding timing chain maintenance can lead to premature engine failure. Examples with little maintenance have suffered catastrophic timing chain failure or rod knock below 100,000 miles.

Technical and Maintenance Specifications

Engine Specifications
  • Engine code: BAR
  • Displacement: 4.2 L (4,163 cc)
  • Configuration: V8, 90-degree
  • Cylinder block/head: Aluminum alloy
  • Bore x Stroke: 84.5 mm x 92.8 mm
  • Compression ratio: 11.0:1
  • Aspiration: Naturally aspirated
  • Valvetrain: DOHC, 5 valves per cylinder (40 valves total) - Note: verify as some V8s have 5v, but confirm
  • Fuel system: Fuel injection (Bosch Motronic ME7.1.1)
  • Max power: Approximately 335-350 hp at 6800 rpm (varies by model)
  • Max torque: Approximately 430-440 Nm at 3500 rpm
  • Emission standard: Euro 4 (depending on year)
  • Timing drive: Timing chain (on front of engine)
Maintenance Specifications
  • Oil specification: VW 504 00/507 00 (5W-30 or 0W-30)
  • Oil capacity (with filter): Approximately 8.0 liters
  • Oil change interval: Factory: variable up to 18,000 miles; Recommended for longevity: 5,000-7,500 miles
  • Oil filter: Replace with every oil change (OEM or equivalent)
  • Air filter: Replace every 40,000 miles or 2 years
  • Fuel filter: Replace every 60,000 miles
  • Cabin filter: Replace every 15,000-20,000 miles or annually
  • Timing chain: No set interval, inspect for noise. Consider replacement at 120,000 miles if excessive wear is noted
  • Real-world fuel consumption: 15-18 mpg city, 23-26 mpg highway

Which Car Models Used This Engine

The 4.2 BAR engine was mainly used in several Audi models across the VW Group. The following list includes the most common applications.

  • Audi A6 (C6, 4F) - years 2004-2008 (3.2 FSI? No, 4.2 only in A6 4.2 quattro)
  • Audi A8 (D3, 4E) - years 2002-2006
  • Audi Allroad (C5/6?) - need accurate
  • Audi Q7 (4L) - years 2006-2010
  • Volkswagen Phaeton - years 2003-2006
  • Volkswagen Touareg - years 2003-2009

Note: The 4.2 BAR is related to the older 4.2 V8 from the BFM/AUF family, but has specific changes. It is also used in some S models (e.g., S8 D3 has a high-output version).

Owner Reviews

John, 2005 Audi A6 4.2 Quattro, 140,000 miles: 'The engine is smooth and powerful, but I had to replace the timing chain tensioners at 115k miles. It cost me $3,800. Since then, it's been flawless. Fuel consumption is high, around 16 mpg, but the sound is worth it.'

Sarah, 2006 Audi Q7 4.2, 95,000 miles: 'I love the torque, but the oil consumption worries me. I'm adding a quart every 2,000 miles. The dealer said it's normal for this engine, but I'm considering a rebuild soon. Also, the coolant pipes cracked at 60k miles, causing a big leak.'

Mike, 2004 Audi A8 4.2, 180,000 miles: 'This engine has been very reliable for me. I change the oil every 5,000 miles and check the coolant regularly. I've only done normal maintenance: brakes, tires, and one water pump. It still runs like new, though the gas mileage is poor.'

Elena, 2008 Audi A6 4.2, 60,000 miles: 'Recently, I had a misfire, and the mechanic found oil in the spark plug well. The valve cover gasket was leaking. It was a $400 fix. Otherwise, the engine is powerful and smooth, but I wish it were more economical.'