For most modern vehicles (2015+) on full synthetic oil: normal driving is every 7,500 to 10,000 miles or 12 months, severe driving is every 3,750 to 5,000 miles or 6 months. The 3,000-mile rule dates to 1970s-80s engines with looser tolerances and conventional oil that broke down quickly; modern direct injection and synthetic oils resist thermal breakdown and suspend contaminants far longer, so following the old rule today wastes money and oil without protecting the engine. Nearly 70% of drivers actually qualify as severe without realizing it - most owner's manuals list a separate Normal and Severe (or Special Operating Conditions) schedule, and severe applies more often than drivers assume.
Regardless of mileage, service the vehicle immediately for: an oil pressure warning light (stop driving immediately, not a suggestion); dark, gritty oil (fresh oil is amber); loud knocking or ticking on startup; or blue exhaust smoke (oil burning inside the engine). One gallon of used oil can contaminate one million gallons of fresh water, so never pour it down a drain or into soil or trash - AutoZone, Advance Auto, O'Reilly, and most municipal recycling centers accept used oil and filters for free.