The Haynes manual's statement that oil capacity is the same for all engines in that year's F-150 is incorrect. Different engines have different capacities. The 4.9L (300ci) inline-six engine in a 1991 Ford F-150 typically holds
approximately 5 quarts of oil.
However, always check your owner's manual (if you have it) for the most accurate information. It's also good practice to slightly underfill when changing your oil and check the dipstick afterward to ensure you're within the proper range.
