It's simply not possible to determine the actual condition of motor oil by looking at it's color.

For example, take a look at this video: Busting Oil Change Myth - link

If you're really concerned and want to set aside speculation, you could send in a used oil sample and get a lab report back that shows the actual condition of the oil and if the engine has any deficiencies you may not know about. For example, excess fuel dilution, dirt intrusion thought the air filter or intake, an internal coolant leak, etc.

Also, nothing wrong with Pennzoil. In the 1930s it wasn't that great, but today it's a good oil. Any name brand oil that's SN/GF-5 rated has good cleansing ability as specified by the API the spec.