The cat, among other things, burns the trace amounts of fuel that don't combust in the engine. For some reason, your engine isn't burning that bad gas, and it'* all flowing into your cat. The extra fuel being burned is making it glow, which is one step away from "very bad."
"Very bad," in case you're wondering, is a clogged (melted) cat. It'* a bit of a stretch, but check your spark plugs and fuel filter. One could have been fouled. Talk to the station owner as well, and find out if they got a bad batch.
(Also, most states have laws against filling the gas tank of a running car. At the very least, it may set a check engine light.)
2007 Pontiac G5
1999 Pontiac Grand Prix GT - Stock engine ate transmission.
1997 Pontiac Bonneville SE - Cammed engine ate transmission.
Last edited by SignOfZeta; 02-22-2010 at 02:25 AM.