Yup, I've heard of the add water test to see if you have alcohol in your fuel, test. However, it's my understanding, that the combination of water and alcohol increases the strength of/or changes it to create a more caustic [ is that the right word?] substance. Its been said on other forum's that alcohol in its own state is relatively safe and won't attack the epoxy's or poly's, however the true proof is when its mixed with some water and left to sit. We all know alcohol has a great affinity for water.. and rarely in a fuel tank will you find zero water and with the alcohol mized in you get this problem. I'm no chemist, and I'm currently working of memory here as my email archives are at home. When I get a sec I'll have to go look it up, but if memory serves me correctly.. there was someone else who did the same test, just with water included and stated they hadn't found a suitable fuel tank sealer or liner [meaning some type of resin coating] which stood up to this combination. Again thats all from memory.