cbaber is right: don't be discouraged by a 1.2 mpg difference! It's a significant amount of fuel & money saved when you're talking about something as thirsty as your van.
You would save $392 a year (20k mi., $3.61 gas) by going from 14.04 to 15.2 MPG (1.16 mpg difference).
fueleconomy.gov mpg/cost calculator: Save Money
If a Geo Metro driver made a 1.16 mpg improvement from a 50 mpg starting point, it would only save $33 a year for the same distance/gas cost.
(There's the problem with talking in "MPG" in a nutshell. But that's another topic.)
Keep going!
