I just bought a nice 2500 Dodge RAM V8 5.9 4X4 96′ rebuilt engine/new tranny. To me It consumes LOTS OF GAS, 14 mpg everywhere and going up hill to the mountains (not towing) maybe 7 mpg. I can’t handle this and It’s not even very powerful (check engine light NOT on). I believe It needs a tune-up although everything seems to work/sound perfect. What Kind of Upgrades should I do to save on gas? It already has a big 4" K and N custom air filter. Should I get spark plugs from the dealer, autozone, platinum , iridium or E3 High Efficiency spark plugs( I don’t want to burn valves). Any programmers? Thank You for your time and your Knowledge !!.