Castrol motor Oil 10w30 cost $2.98 a quart and theres the stores bran that cost $1.50 a quart. which is better

The store brand meets the minimum standards for engine oil and will be quite OK. Some of the major brands may and I say may have additional additives that make the oil a little better. When you buy a major such as Castrol, you're buying a name. If you really want a better grade of oil, the synthetic blend is little better but the 100% synthetic is a lot better. Again, the store brand is the way to go.