03 dakota sport 4.7, 5 speed 4x4, regular cab. I always got 18.5 mpg, give or take a .5 gallon. 350-380 miles per tank. Now I am only getting around 250-270 miles a tank. What should I look for? It has 120,000 miles, recent plugs and airfilter. When I tow it ranges from 12.5 to 14.5, that has not changed. Any suggestions.

 

there could be a number of things, but start off simple by adding a high quality fuel injector cleaner or seafoam your engine. I was also getting horrible fuel mileage on my '95 V6, I went from 19 mpg overall to 15-16. I used seafoam (1/3 bottle in the tank, 1/3 in the oil & 1/3 induction) and I went back to 19 mpg overall with 22 highway. Also the grade of fuel you use will also have an effect. I never use 87 because the last time I did, my truck ran like crap.

 

the grade of gas really doesnt change too much actually, my auto teacher just explained that to us. you will run higher octane with higher viscosity oil. but everyone has their own opinions on gas grades. i would say do the sea foam treatment, or check the fuel filter.

 

Fuel quality is a huge issue especially with driveability issues. Ask your auto teacher about winter grade & summer grade fuel and the effects running winter grade fuel in warm weather does for driveability. Ask him also about RVP (reid vapor pressure). If he's like me (ASE Master Certified Advanced Level Engine Performance Specialist) he'll know exactly what I am talking about.

Also, since all 50 states have mandated that we use 10% ethanol, fuel mileage has gone down on average by 15%. Ethanol destroys rubber components, causing water to seperate from fuel so when you have a low tank of gas (below 1/4 tank) depending on where you live you could be sucking up water in & burning it. There are fuel additives that help the ethanol concentration, like Lucas.