API rating generally refers to the standards set by the American Petroleum Institute for oil quality (well... something like that). The higher the API rating (in alpha-numeric), the better supposedly the oil is, especially for newer engines. CMIIW.

The higher ones nowadays is CI-4 for diesel oils and SL for gasoline engine oils.

The Valvoline you're looking at is already dated based on it's API ratings, you can try checking out other mineral based oils like Petron Touring (SJ or SL) 20W-50. Higher viscousity oils are recommended for older/high mileage engines and for hot/humid weather climates.

If you're on a budget (well nowadays who has the luxury of extra cash?), it's still better for your pocket and your engine to stick to regular oil then change regulary (every 5,000km).