I am often asked this question. It's a question that has been asked since the beginning of time, almost as much as "What's the meaning of life?"      I jest of course. The answer is...It depends. The old standard answer used to be every 3000 miles. Auto manufactures now recommend between 5k or 7k miles. Some go as high as 10k miles. The true answer should be, "How long do you want your car to last?" Do an oil change at least every 4000 to 5000 miles and your car will last a long time. Use synthetic oil and not only can you push the change interval out a couple thousand miles, but your engine will last even longer. Oil changes not only make your engine last longer, but it improves gas mileage and the engine runs cleaner. Both are good for the environment. And by the way, all waste oil and filters collected by Tri-Valley Automotive are recycled.