the previous owner installed an oil pressure gauge in the car which isn't connected to anything, except the positive and negative to look nice and shiny, and I hate having things not working in my car, so I need to know the thread size so I can get myself an oil pressure sensor (that can run a gauge, not the on/off type) to run the gauge off it.
Edit: Also as I'm so close to an oil change, I don't want to remove one to confirm the thread size, then have a week without the car before I get my hand on an oil pressure sensor :/