"Quicky oil-change shops may urge us to change the oil in our vehicles every 3,000 miles. But most cars nowadays don’t need changing that often. In fact, most manufacturers say you can go 7,000 miles without a problem. Ditto for that SUV—unless you really are starring in one of those TV ads and driving it hard and long over dusty roads."
"What difference does it make? Consider this: each year California alone generates about 153 million gallons of used oil. Change less often and it really can save your engine and the planet."
Courtesy of the Green Life from The Sierra Club