"On second thought"
After looking at bearing failure causes on several additional websites and thumbing through even more repair manuals, I am tending to agree with Hanley and Russ that this is more likely a case of bearing failure caused by extreme engine lugging. Recently another A4 owner who posted bearing pictures with similar pitting marks, was also experiencing an inability to reach decent cruising rpm's, which would also tend to support this theory. Although Acid corrosion does look similar, the higher wear pattern on the portions of the bearing shells toward the center of the engine might very well indicate a "flexing" of the crankshaft. Ironically, the better the tune of the motor, the more this situation would be prone to happen.
Tom
After looking at bearing failure causes on several additional websites and thumbing through even more repair manuals, I am tending to agree with Hanley and Russ that this is more likely a case of bearing failure caused by extreme engine lugging. Recently another A4 owner who posted bearing pictures with similar pitting marks, was also experiencing an inability to reach decent cruising rpm's, which would also tend to support this theory. Although Acid corrosion does look similar, the higher wear pattern on the portions of the bearing shells toward the center of the engine might very well indicate a "flexing" of the crankshaft. Ironically, the better the tune of the motor, the more this situation would be prone to happen.
Tom
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