Tygon and at least some of the aquarium tubing that is available are polyvinyl chloride (PVC). (Silicone tubing is also used for aquariums as well as the polyproplyene or polyethylene mentioned above) Although reasonably resistant to gasoline, the plasticizers (phthalate esters) are extracted from PVC tubing over time which will make the tubing stiff or even brittle. Polypropylene (and polyethylene) tubing are much more resistant to gasoline over a longer timeframe but generally less flexible so it may be more difficult to negotiate sharp bends in routing the lines. Polypropylene will not give as good a friction fit to a barbed connector because it is less elactic than other types of tubing (PVC, silicone, neoprene). Leaks at fittings will be a bigger problem.

Ross