Which has better miles per gallon?
It would be better rated on the MpG per Kilo carried. Your Motorbike may have a great MPG but can only carry a small amount of weight, IE you and a pillion passenger. The transit can carry 3 sweaty builders and their tools, bricks, planks of wood etc. so technically the Transit would be more economical as it may do 26mpg for 3500kg while your bike may do 60 MPG per 250kg. But the answer would be, Use the best tool for the job, Going to the shop for some Fags and the Daily Mirror, Ride the pushbike. Going to visit Auntie Sue 20 miles away for tea and cakes, whilst dressed as a Power Ranger, Ride your Motorbike. Going to Build a Conservatory , and taking all your tools and supplies and another two Daily Mirror reading builders who have a tendancy to shout at the girlies out of the window with you, the Transit would be first choice.