I think the "clunk" is the most irritating "problem". It must be our third world roads in Kaneohe, especially the concrete bus pads and tree roots causing v-shaped "speed bumps" in the roadway. My friend's 29yr old 911 doesn't make these kinds of noises. Of course, you can't hear anything in it because there's no AC and the engine is wailing away.
Keith (service manager) wasn't concerned about the coolant level, said not to worry until the warning light comes on. Yeah, sure.
I think my (good) mileage is due to: 1) it's a 2.7, 2) I use the H3 (only 6 stop lights between home and work), 3) the time I drive to work (6am), 4) and runs out to Makaha (golf) and Waipio Costco (short lines, nice big parking spaces). This is in spite of my: 1) keeping the rpms above 3K, 2) not using 5th gear very much, 3) driving to/from our headquarters downtown from my office near the airport.