Usually 1" or 1 1/16". A deep well thin wall socket will work on most vehicles. Lisle Tool # 13250 or KD Tool # 3458 will get it done on GM Vehicles
The oil pressure sending unit and the oil sending unit are the same. It is located almost directly under the alternator. Remove the alternator and removal is simple when you have the correct socket.
The oil pressure sending unit is located on top of the motor beside the base of the distributor. You will need a special socket from your parts store to remove/install the sending unit without harming the new one. The socket is not expensive and does fit sending units for other cars.
What size motor?
An oil pressure sensor socket.An oil pressure sensor socket.
Unplug the electrical connector and slide the OIL SENDING UNIT SOCKET down over it and screw it out. It is a special socket. If you have the room you can screw it out with a pair of pliers.
The oil pressure sending unit is located on the oil filter housing. Look above the filter and you will see a single wire going to the unit. You will need a sending unit socket to remove it. The tool can be purchased at any auto parts store for a nominal fee.
That requires a special socket made just for oil sending units. Your local auto parts store can sell you one.
Need more info as to which sending unit, oil pressure, coolant temperature or fuel level.
The easiest way would be to purchase the special socket that fits that sending unit to remove and install.
Remove the oil pressure sending unit retaining ring. Remove the wiring harness from the sending unit. Poll the sending unit out of the engine.
On the 4.7 V8 it is above the oil filter, you'll see the wires going to it.I checked and it is a 1 1/16" deep socket for the sending unit.
Were is the oil pressure sending unit on a 95 mitsubishi miaage