I question the advice on filling up while half empty. While it makes some sense in a storage tank, you have to remember that a gallon of gas probably weighs a little more than 8 pounds. So with my 18 gal tank, I would be lugging around at a minimum at all times, 9 gallons (following that advice) which then equates to about 75 pounds.
I wonder if you really end up saving then on that tip or actually losing out...
