Oil Brands?

just have a quick question for those who want to comment. I was in the auto parts store today to get oil and a filter. I uasually get castrol gtx or penziol. There about 18 bucks (cdn) for a big 5l jug. Then i saw the cheaper stuff, it was 7 bucks for the same ammount of oil and it had the "stamp" (gold star) on it. Just wondering if theres actually a difference between the fancy brand-name stuff compared to the cheap stuff? thanks.