Wanted to add that I finally had a chance to change the oil and put in the Synpower 5W-20.
Kind of a minor adventure:
I was thwarted every time I wanted to change it in the past week--got stuck working late, then too dark and too tired. Wanted to do it Saturday. Discovered my ramps (made of 1/2" steel stock by my dear departed grandfather and sturdy enough to hold the space shuttle) were too steep and would destroy the car's air dam if I used them. So a trip to Harbor Freight for ramps--these had a better slope, but the heavy RWD car would push them down the driveway instead of climbing them. Another trip to O'Reilly and bought some better ramps for only a couple dollars more. I like these--they are plastic too, but wider and with rubber feet. But alas, the car still pushed them down my driveway, albeit a little different---the car would climb them a little, then shoot them out from under the front tires like watermelon seeds.
So another trip out to Lowe's for something rubber that I could put under them and keep them from sliding. Wouldn't you know that the Lowe's employees I talked to claimed to NOT have any kind of rubber pad I could use in their entire cavernous store... So I wandered around through roofing, hardware, etc., having no luck. Finally happened across some recycled rubber entryway mats that looked tough enough to stop a small-caliber bullet for about $8/each. These did the trick and I was able to get the car to mount the ramps with no problem, but had to call it a night until Sunday, as getting dusk again.
Despite the dealer saying that he'd changed the oil per my request and me having an invoice with "oil changed per customer request" with no other info, I was skeptical. The oil didn't look bad, as I mentioned in the OP, but when I drained it, it was pretty dark.
Apparently Hercules had tightened the drain plug, as I had to rap the socket handle to break it loose. The filter was almost as bad and took some time to get to turn as well. Added 7 quarts of Synpower (prefilled the filter before installation), turned the key, and had oil pressure almost instantly with no mechanical noise.
Driving it, the car feels more responsive on the synthetic and oil pressure is slightly lower at idle and slightly higher at midrange RPMS. Seems to indicate a used-up, thickened oil was in there to me, or perhaps the wrong viscosity. (18PSI hot at 560RPM, 50-60@3000+ Motor is quiet, with only the very barest hint of the infamous "Hemi tick" that you have to really listen for at idle. So I'm overall pleased with the results.
Just wanted to follow up... Thanks all.
