* Engine: Bolt sizes for the engine block, heads, manifolds, etc., will be numerous and vary in size and thread pitch (e.g., M8, M10, 3/8"-16, etc.). You'll need a repair manual specific to the engine in your Cutlass Supreme (e.g., a 3.1L V6, a 3.8L V6, or a V8, if so equipped) to find this information.
* Wheels/Tires: The lug nuts on the wheels are likely a standard size, often 7/16" or 1/2" but you should always verify this with your owner's manual or by checking the size stamped on a lug nut. Using the wrong size can damage your wheels.
* Suspension/Chassis: Numerous bolts secure various suspension and chassis components. Again, a repair manual is essential for determining the correct sizes.
* Body: Bolts holding body panels, interior components, etc., will vary wildly.
In short: You need a repair manual specific to your 1990 Oldsmobile Cutlass Supreme to determine the sizes of the bolts you need. Trying to guess could lead to damage or injury. A Haynes or Chilton manual would be a good place to start. You can also find online resources, but be sure they're specifically for your year and model.
