Why are people still changing ther oil every 3000 to 5000 miles. In a recent Lubricants World Magazine interview the president of a major national quick lube chain (which is owned by a major petroleum oil company) states that if they can get customers to shorten their drain intervals by 100 miles it would mean an additional $20 million in revenue for the company per year and if they can get consumers to do one more oil change per year it would mean $294 million for the oil change alone and $441 million in revenue when they include ancillary products and services that go along with the oil change. In fact, the president of the quick lube chain openly admits that the bottom line is profits. The shorter the drain interval the more money the quick lube makes. It is our opinion that they would be more profitable by promoting and installing AMSOIL 25,000 mile/1-year or 35,000 mile/1-year extended drain interval synthetic oil. It appears that the short drain interval petroleum oils they promote are good at assuring that customers will be back for another oil change in a relatively short period of time. I do your first oil change with no labor charge. Just the price of the oil and filter.