Modern oils are used for a variety of reasons, they are more stable than "Standard" mineral based cheapo oils, they lower emissions, are more fuel efficient, they also allow for less oil to be used in the engine, reducing weight, less upfront purchase costs, less oil to dispose of in the environment etc. So I would always recommend you pay the least you can for better quality oils, a 5W 30 mineral oil will work well, but not as well as a synthetic based oil with a lower viscosity