Thanks, MB Doc, Fred & Harry.

I've had 10,000 mile oil changes done by the dealer using Synthetic 0-W40. My usage is almost entirely on the highway at 70 mph. The car is in the shop now for another oil change. I hope things are improved. The cat issue is intriguing. I will call the dealer and ask him to check.

Thanks again for your support. I hope to hear more good advice from the forum.

Cheers,

Steve