I want to improve gas mileage on a 95 GMC 350 5.7 Vandura Starcraft conversion (weighs under 6,000 lbs)
Just bought the above and only get 12 mpg. Came with stock parts. I have done the usual, new spark plugs, wire, hoses, air filters but am wondering what more I could do to increase mileage. I had hoped to take a coast to coast trip and back in it.