I have both 5-minute and 30-minute epoxy on my firewall, and the 5-minute version has turned yellow and cracked, with fuel underneath it (I use 20% nitro). Maybe the only fuel proof 5-minute epoxy is Z-Poxy. Here is another thread on this topic: [link]http://www.rcuniverse.com/forum/m_1516662/anchors_1520745/mpage_1/key_fuel%252Cproof/anchor/tm.htm[/link]