GAMI Answers G100UL Criticisms Point By Point

What do you mean by “rubber”? The real thing, the natural stuff? Gasoline of any sort will destroy that. In terms of synthetics, you can get formulas that will resist any of the common chemicals such as those found in G100UL.
In most light airplanes, there aren’t all that many rubber fuel lines to replace, and those are a replacement item in any case.