The best way to know exactly when to change your car engine oil is to check your vehicle’s owner’s manual first — it provides the manufacturer’s specific recommendation for your make, model, year, and engine type. Most modern cars (especially post-2015 models) use full synthetic oil and can safely go 7,500–10,000 miles (12,000–16,000 km) or 12 months, whichever comes first, under normal driving conditions.