However, common oil weights for that era of Suburban would be:
* 10W-30: This is a very common and often recommended weight for a wide range of temperatures. It's a good all-around choice for many 1991 Suburbans.
* 5W-30: This is a thinner oil, better suited for colder climates. It provides easier starting in cold weather.
* 20W-40: This is a thicker oil, often preferred in hotter climates or for engines with higher mileage.
To find the correct oil weight for YOUR 1991 Chevy Suburban, you MUST consult your owner's manual. The manual will specify the recommended oil weight based on your specific engine (e.g., 5.7L, 6.2L, 7.4L, diesel). Ignoring this could harm your engine.