* 7.3L Power Stroke: The oil capacity for the 7.3L Power Stroke is typically 12 quarts with a new filter.
* 7.8L Gasoline: This engine would use a significantly smaller amount of oil; you'd need to consult your owner's manual for the exact capacity. It's irrelevant in this context given the question specifies a *diesel* engine.
Therefore, assuming it's the 7.3L Power Stroke diesel, the oil capacity is approximately 12 quarts. Always double-check your owner's manual for the most accurate information specific to your truck.