The amount of oil a Chevy Workhorse engine needs depends on the *specific* engine. Workhorse is a brand of chassis cabs, not an engine. The chassis cabs can be fitted with various gasoline or diesel engines from different manufacturers (like Duramax, Vortec, etc.) each with its own oil capacity.
To find out how much oil your Chevy Workhorse needs, check your owner's manual. The oil capacity will be clearly stated there. You can also find it often on an oil fill cap or dipstick.
