My question is in reference to a '08 Nitro, 3.7 V6. the truck has 64,000 Miles on it and no engine codes are showing. since having the car it has always given decent fuel mileage, 22-25 depending on the wind and hills. it has for the last month or so mileage has dropped to around 20 at best. I have changed the plugs and the K&N air filter is clean. I always use Shell gas and there have been several tanks of fuel run through it. Anyone have any Ideas or experienced this problem. Thanks, Charlie