I have a car that recommends premium. I have never used it, so I was putting regular in. I noticed that it was running rough, so I started putting the fuel treatments in like techron and the one in the white bottle. That made it run much better. Talked to the mechanic and he told me to use premium. I've switched over, and my car purrs like a kitten. He told me different engines are tuned to a specific octane level. Put in what your car recommends. Also, its good policy to buy from the major brands rather than the cheapest stations. The major brands put in additives to make the engine run cleaner. That advice comes from a long time gas station owner.