Your dad knew that Frequent oil changes were the key to keeping his Buick on the road another year. And while owner’s manuals for today’s cars recommend increasing long intervals between oil changes, the fact remains — frequent changes flush abrasive dirt and metal particles out of the engine, prolonging its life. Most owners’ manuals recommend a more frequent interval for “severe conditions.” To maximize the life of your engine, follow the severe intervals recommendations, especially if drive regularly in stop-and-go traffic.