Are all car engine oils basically that same and, if so, does brand matter? Every oil you see on the store shelf meets the basic specifications for that weight oil (5W30, 10W30, etc) and is suitable for use in your car provided it is the correct weight as recommended by the vehicle manufacturer. That being said, a large part of the cost of engine oil is the additive package to the basic oil stock that will determine how resistant the oil is to thermal breakdown and how well it lubricates the engine. Premium oils tend to have better (more expensive) additive packages that enhance the lubricating and thermal resistance properties of the oil. This, in turn, means these oils tend to cost more than non premium oils.
At Wayne’s Automotive and Xpress Lube our standard oil is Castrol which is premium oil. It does cost more because of the additive package, but the better lubricating properties will most likely result in gas cost savings that more than offset the higher oil cost. Additionally, since Castrol is more resistant to thermal breakdown it provides better engine protection.
Synthetic oils like Castrol Syntec provide even better protection against thermal breakdown meaning you can change the oil less frequently. If your car requires oil changes every 3000 miles, you can safely increase that interval to 5000 miles using Castrol Syntec. Syntec also provides better lubricating qualities that should improve your gas mileage as opposed to using non-synthetic oil.