I use shell 87 octane 90 percent of the time in my di Hyundai. The car calls for 87 so that's what I use. But I also have used mobil and exxon and citco and Sunoco. Now I know mobil and exxon are top tier besides shell but every now and then I use Sunoco because its closer. I think someone hear posted a while back that exxon actually has more detergents in the 87 octane then any other gas. Not sure if that's true. All I know is that all the gas stations around hear get there gas at the same terminal across the river from me. Is there that much of a difference in gas nowadays. Doesn't all gas have to meet certain standards. Can the owners of these stations be cheating on the amount of detergents they use or is it all part of the terminals computer system when they pump to fill the trailers. Ill have to ask my brother when I see him. He used to haul fuel a lot. He once said that gas was gas. But that was a few years back.