I have been using various generic or house brand 15W40 and 10W40 oils the last few years in my cars with good results. I suspect most generics are made by major companies just using different containers. I also pick up major brands when the price is right. For example, the dollar store where I live has Shell 10w40 every day at 89 cents a quart. I have been changing at 4K but I am going to 5K intervals since my usage is not real severe. Seems like most of the people who recommend 3K intervals are in the business of selling/changing oil. Just my 2 cents.