* Oil: 5W-20 is the most commonly recommended oil viscosity for this engine in most climates. However, your owner's manual might specify a different viscosity depending on your location and expected temperatures. Always use an oil that meets or exceeds the Ford specification (check your owner's manual for this). Many people use synthetic blend or full synthetic oils, but conventional oil is acceptable as well.
* Filter: This is where checking your owner's manual is crucial. The correct filter depends on the specific version of your 4.0L Explorer. There are multiple filter types that could be compatible. You'll find the correct part number in the manual or a parts store using your vehicle's VIN. Popular brands include Motorcraft (Ford's brand), Fram, and Purolator. Using a filter that's not designed for your engine could lead to problems.
Do not solely rely on this information. Always consult your owner's manual for the precise oil type and filter part number recommended by Ford for your specific vehicle. Using the wrong oil or filter can damage your engine.
