Vehicle owner manuals provide recommended engine oil specifications directly from the manufacturer of the vehicle. Online websites specializing in vehicle fluids, such as FluidCapacity.com, also have searchable databases of vehicle oil recommendations.
Vehicle owner manual recommendations are designed for new cars that are still under warranty. Using a motor oil that is not recommended may invalidate a manufacturer warranty and result in poor engine performance. Professional websites and mechanics sometimes advise to switch oil specifications in older vehicles, as the original recommended weight may not sufficiently lubricate worn engines. Temperatures can also affect which oil is recommended, and customers living in extreme weather conditions often need to use multi-weight oils to cover extreme high or low temperatures.