The recommended oil viscosity for a 2008 Ford Fusion 4-cylinder depends on the ambient temperature. Ford typically recommends using
5W-20 for most operating temperatures. However,
5W-30 might be acceptable in hotter climates or if you're experiencing higher mileage and increased engine wear.
Always check your owner's manual. This is the definitive source for the correct oil viscosity for your specific vehicle. The information printed in the manual will supersede any general recommendations. The manual will often have a chart specifying viscosity based on temperature.
