This is ludicrous...
It's the same logic as telling your kid to drink half a glass of milk twice a day instead of a whole glass of milk once a day, and convincing them that they are drinking less milk...
The oil companies don't care how SLOWLY you fill your tank, if you're driving the same amount. In fact, filling up your car slower insures that you will be paying the highest possible prices all the time. When the price goes up, you go the pump and fill up HALF your tank. Then the price goes up again, and you fill up the rest...
Here's a thought. CAR POOL. GET A BIKE. WALK. BUY A CAR THAT GETS BETTER MILEAGE.