Regular oil changes, roughly every 5,000 miles, are the single most cost effective way to preserve the performance life and value of your car.

In most cases it doesn’t have to be religiously changed every 3000 miles. That number helps sell oil changes. You really should check your oil at least every other fuel fill-up. Some cars can burn enough oil to be dangerously low well under 3000 miles.
A number of manufacturers are recommending 10,000 to 15,000 mile oil change intervals. Hmm… It seem they mean to sell you a new car before its time. Some cars have “lifetime” transmission fluid. What? Who’s lifetime? The now shorter lifetime of the car, or of your lifetime, or is it some indeterminate lifetime of the transmission fluid?
Modern cars CAN be made to last. Regular engine oil and fluid level maintenance is a key to longevity.
Many newer cars, especially those with lighter oils like 0W-20, were designed for maximize fuel economy. One way to increase miles per gallon is to reduce friction and a way to do that is to reduce the tension in piston rings. Lower tension means these rings, which help scrap down the oil from the cylinder walls, don’t create as much friction. With less friction, old contaminated oil can gum up and eventually make these piston rings not do their job. The engine starts burning way too much oil, the oil level drops, runs hotter, and creates a vicious cycle that eventually destroys the engine.
Regular oil and filter changes are the most effective means for keeping your engine going and going. So what oil do you use, how often do you change your oil? Most knowledgeable mechanics and tribologists (scientists who study oil and wear from friction and associated chemical affects) say changing engine oil at 5000 miles with almost any conventional oil is better than using the finest synthetics and waiting for 10,000 or more miles. Using synthetic oil is best. Do you have a car with lots of miles that you’d like to keep? Oil blends exist with special additives meant for engines with lots of miles.
Unless there’s an actual design flaw (which does happen with some engine models) many modern engines can last 300,000+ miles.