Oil question

20W-20 is is a straight grade that was pretty popular until the '80s. Straight grades were cheaper, so even though there were more advanced products they did their job and were a good value. The reason it looks like a multi-grade is because the SAE has both a maximum thickness when cold winter rating and minimum thinness when hot summer rating for grade 20. So an 20 oil that met both criteria could be labeled 20W-20 to show it.

HD can mean high detergent, heavy duty, Harley Davidson or whatever you want. Grade 60 was, and maybe still is, a popular oil for V twin Harleys and Indians, and Top Fuel and Funny Car racers. SAE didn't define a 60 until the '90s. So anything heavier than the spec for SAE 50 was called Grade 60. For cars 1967 and older probably means it has an API SC rating. Pretty low detergent levels. The current rating is SP. So that's a lot of updates since then. Pennzoil did sell a API SC grade 30 until the late '80s. We called it "regular 30." It also said for 1967 and earlier on the can. It wasn't a big seller and was discontinued.

If you can post up clear pictures of labels I can probably help you with a lot of your questions.