How much were you making though? $1/hr? Comparing personal historic prices, I think it's better to compare how long you'd have to work to buy $product. Assuming you made $1/hr, you had to work 15 minutes to buy that oil. Minimum wage today is $7.50 I think, and you can get 5qt of full synthetic oil at walmart for $16, so that minimum wage worker would have to work 26 minutes to buy a quart of oil. Is that bad? Full synthetic is better than reconstituted single weight oil. Might be a bit better or worse, but I'd call it a wash I think.
edit:
I just looked it up, and it appears minimum wage was $2.30 in 1976. I don't feel like running the numbers again, but it makes walmart oil look a little worse. Interestingly, minimum wage was only $2.50 when I started working in the 80s. Ten years only got another 20¢ :^/
edit2:
My memory sucks. Looked up 1985, and it says minimum wage was $3.35. Could have sworn I made $2.50 at the bakery. Everything's an illusion!