[chuckm]

Okay, let me drop a different idea. What if you had a vehicle powered by propane (or LNG for that matter) instead of gas? Tap off the bottom of the propane tank and run the liquid fuel through the AC evaporator set prior to sending it to the engine. When you are not using the AC, use exhaust gas to warm up the evap. In fact, you could use the exhaust gas to preheat the propane to the optimal combustion temp as necessary.