If the new fuel is acting on old rubber etc in as litttle as 12 hours we all might be in big problems. I liked the last posters suggestion it may have dissolved residue in the tank basically. This is the first I have heard it might also be a powerful solvent as well though. This quick acting if so is not good. The present expectations are for the oil companies to do basically nothing. At some point the best we might hope for is they will no longer claim it is harmless if they are still using the line of compatability at all.