High-quality gas at a lower price? A fuel and finance expert helps us explain why Costco gas is so darn cheap.

These are basically Costco gift cards worth a percentage of your trip cost as a bonus. So if you spend $6,000 on a vacation ...

The gas stations at Costco warehouses are "open to Costco members only," with Costco Shop Card customers also able to purchase fuel, according to the retailer’s website.