I changed the oil in my mother-in-law's '02 Tahoe on Saturday & noticed something interesting in her owners manual. The 5.3L engine in her Tahoe is a flexibile fuel engine & is designed to run on either unleaded gasoline or up to 85% ethanol fuel. I've never seen an engine like this before. (probably because I live in AL) Where would one find 85% ethanol fuel? Is that the stuff that's made from corn? What would be the pros & cons of running ethanol fuel? Thanks in advance.