In regards to the Rad Cap releasing pressure, they DO fail over time and if it fails and there is a pressure spike... boom, elbows bust. Seen it happen before. The elbows are easy to change, you just have to make sure when you get the old ones out you get it all cleaned up or there is a potential for a leak.

GM# for the elbows are #24503243 - $12.97 retail & #12565082 - $3.98 retail. Any local GM dealer should keep several on hand as they get replaced ALOT.

I personally use the Mobil1 5w30 in the snout and know several others who use it in their. It does take 8 oz and IF you can get it from a local dealer you can, but if not (like me, no local dealership sells it and I don't want to order a case), you CAN use it without problems. Been 30,000 miles so far without issue, just change regularly. Also as with any oil, after so long it will start to break down and that is why it shows to be low. It also goes in clear, but comes out dark brown and stanky after 75,000+ miles.