[Flyinghigh]

I use Mobil One in my Chevy and it's not even a turbo. I wouldn't put Pennzoil in my lawn mower, but that's my personal choice. How many miles are on your Caliber? If it's a lot, you might add a couple of ounces of Seafoam to the oil before you change it and see if that helps your "valve noise".

 

[Flyinghigh]

You're also around the mileage that a lot of folks have had trouble with the alternator decoupler pulley going bad. Maybe you're hearing the first sounds of that sucker going out. Do a search hear and you'll find several videos of that. You can also fashion a cheap stethoscope with a funnel and piece of heater hose. Attach the hose to the funnel, put the hose on the alternator with it running and put the funnel up to your ear. If it's knocking or tapping, the funnel will amplify the noise. Just be careful not to let the hose get into the drive belt!

 

[Flyinghigh]

I doubt that it's a valve, since you haven't noticed it in a few days. Valves don't just "start to go" and then quiet down. They get progressively worse if one is burnt. Maybe put a couple of ounces of Seafoam in the crankcase, drive it a day or two and then do an oil change with a good synthetic you like and a QUALITY oil filter.