Automobile manufacturers have taken to making recommended service interval of 5000 to 7500 miles. This is because it is in their best interest that you buy a new vehicle sooner. I, as an individual in the service industry, can tell you first hand that the manufacturers of the products used in/on these vehicles are much more likely to give you a more realistic picture of how long THEIR products will last. Conventional oil manufacturers recommend that you change your oil every 3000 mile or 3 months, whichever comes first. They dop this for a very good reason, the oil is no longer providing you engine with protection after these intervals. Synthetic oils are great, but still only last 5000 mile or 4-5 months. The auto manfucturers base their intervals on the idea that you are driving you vehicle under non-severe conditions. In reality, less than 1 percent of drivers actually operate their vehicles under non-severe conditions. And in reality, it does not matter, fluids, although ultimately much better engineering is used to design them than 10-15 years ago, ultimately break down under a certain amount of use and time, regardless of the conditions under which they are used. Coolant is still coolant, and even extended life coolant(which is recommend that it ONLY be mixed with DISTILLED WATER(otherwise it's deterioration rate speed to that of conventional coolant or faster))is a product that was engineered with a novell purpose, it does not usually live up to it's expectatations(in fact often the dealers themselves seldom use the distilled water to mix these coolants, but will try to convince you of the semi-permanence of the product, and tell you you do not need the fluid serviced yet. But, they WILL sell you this prouct at a PREMIUM PRICE!) To be continued...p.s. pleae vote below!