1999 Jeep Cherokee Spark plugs

Thank you very much Joe for your answers, well about the reason I change the spark plugs every 3 months is becuase If. I don't my gas mileage goes down and I have done that for a while and it's working I tried to hold the plugs for five months once and that's when I notice the gas situation, I got my tires check every week also I got one of those air filters k&w? I can't remember right now but, it's been really good air filter and when I do change the plugs the gas mileage goes up again, so if you may think another option that I may include to don't have the plugs change every 3 months and gave a good gas mileage at the same time I will thank you for that.
Best regards;
Carlos Barragan.

Hi was reading your post on spark plugs what is the mileage you get from new plugs after 3 months compared to 30,000 miles, would the price of plugs make up for the cost of gas Getting the most from your gas? - It is no secret gas prices are up and putting a big pinch on our pocket books. Car maintenance and driving habits significantly affect fuel economy. Here are a few tips to help you get the most for your buck. First, check the air pressure in your car's tires. Most vehicle tire pressure recommendations are located on a sticker in the driver's door jam or on the side wall of the tire. While tire and car manufacturers recommend a prescribed tire pressure, it has been shown that slightly more tire pressure is optimal for achieving higher fuel economy by reducing rolling resistance. Some hybrid cars are manufactured with tires that can hold up to 55 P.S.I. As compared with the usual 32 P.S.I. For safety and better gas mileage always keep your tires properly inflated. Next, analyze your driving habits. Do you take off quickly from a stop? Try easing into the throttle and allow the vehicle to accelerate slowly. Observe the traffic and signals in front of you. If a stop is imminent release the gas pedal and allow the car to coast the remainder of the distance before using the brakes. Proper maintenance of your car's engine is essential for optimum performance. If your engine is misfiring it will decrease mileage. If the engine oil and filter changes have been neglected it will cause additional friction inside the engine and hinder the performance and gas mileage. Finally, remove all un-necessary objects from the car, added weight can decease mileage also inspect your engine service records and perform a tune up or oil change as recommended. Following these gas saving tips can increase your mileage and save you money.

Are your spark plugs dirty when you change them? Im thinking there may be another problem besides spark plugs.