The foam is to prevent a wide spread fule spill if the tank ruptures in a shunt. It will still burn, but slower since the quantity of vaporized fule is less, at first at least. The theory is that the corner guys with the extinguishers will get there in time to snuff the smaller fire, and the driver only gets roasted a little. Since there are very few guys with extinguishers standing on street corners or on the side of trails, I never lusted for it in a street/off road rig....

Not responsible for advice not taken...