Oh, dude, the thermostat housing on a 1991 Oldsmobile 88 Royale is like that one friend who always hides in plain sight. It's actually located on the engine, near the water pump, and connected to the upper radiator hose. So, if you're looking for it, just follow the hose and you'll find it chilling there, doing its thermostat thing.
Follow the top radiator hose to the engine and find a bulborous part device the hose is attached to. The thermostat is inside there.
Inside the fuel tank.
Word the question properly. What is an Oldsmobile Royale?
no
under the coil packs which are located at the rear of the motor on top
check the fuse box panel
Mounted on top and inside the fuel tank.
Most GMs of that vintage with a power trunk release is located in the glovebox
In almost every engine, the oil pan is located at the very bottom of the engine.
on the block between the oil pan and trans pan
The correct tire size for a convertible 1972 Oldsmobile Delta 88 Royale is 225/75 R15.
The 1989 Oldsmobile Regency fuse box is located beneath the drivers side dashboard. The fuse box will be near the emergency brake release.