I have been using Chevron 91 octane since I started using lawn equipments. I change to Shell one time. The gas smell very different. The Chevron smelled more alcohol where the Shell smelled more karocine( spelling??)!!! Anyone notice different smell of different gas? I am going with Shell because I think alcohol have less lubricating property than gasoline!!! Any suggestion what kind to use, I wonder the composition of gas are the same in different states.