There's speculation on some of the Audi sites about cylinder wall scoring on the 4.2L V8. No real pattern has been established, as both well-maintained vehicles and those with unknown maintenance (used cars) have developed the problem.
Borescopes and tear-downs have indeed confirmed scored cylinder walls. It typically begins with extremely high oil consumption (1qt per 500 miles or worse) and ends with a motor replacement. It's an all-aluminum motor.
One leading theory is that piston swell is the culprit. Quite literally, the space between the wall and rings is fluctuating as the engine turns and the piston is being forced into the cylinder wall.
I understand that changing oils will never fix a manufacturing problem, but is it possible to slow this process with a thicker oil? Are there any additives that could assist? The motor is spec'd for VW 502/505, which is ACEA A3/B3 oils (HTHS > 3.5) that are heavy Xw30 and light Xw40. Typical sump size is 9L/9.6qt.
I am pushing those affected to reply with the car's maintenance history and driving habits, namely the oil type and change interval. Not much data as of yet.
Borescopes and tear-downs have indeed confirmed scored cylinder walls. It typically begins with extremely high oil consumption (1qt per 500 miles or worse) and ends with a motor replacement. It's an all-aluminum motor.
One leading theory is that piston swell is the culprit. Quite literally, the space between the wall and rings is fluctuating as the engine turns and the piston is being forced into the cylinder wall.
I understand that changing oils will never fix a manufacturing problem, but is it possible to slow this process with a thicker oil? Are there any additives that could assist? The motor is spec'd for VW 502/505, which is ACEA A3/B3 oils (HTHS > 3.5) that are heavy Xw30 and light Xw40. Typical sump size is 9L/9.6qt.
I am pushing those affected to reply with the car's maintenance history and driving habits, namely the oil type and change interval. Not much data as of yet.