A 1986 Chevy Silverado should use
conventional ethylene glycol-based antifreeze/coolant. However,
it's crucial to check your owner's manual for specific recommendations. The manual will specify the correct type and concentration for your truck's cooling system.
While ethylene glycol is the standard, the manual might specify a particular brand or a certain level of protection (e.g., a specific freeze point). Using the wrong type could damage your engine.