ok i give in I have no idea how they work, there's just one wire type connection, shielded by a spring type thing

as far as i know the wire and thermo couple is full of wax which expands as it heats up which then mechanically moves the needle

Thats not a wire! Its a capillary tube.

There is a take off where the oil pressure sensor would be on the engine and a tube is fed from there into the back of the gauge which contains the sensor.

Now becoming a period accessory!

but wouldn't the oil be a lot cooler by the time it gets to the gauge? and its just a single tube to the gauge isn't it? so there can't be any flow round it... hmmm
?

It works on pressure IIRC as the gas/liquid inside the bulb (sensor end) gets hot it expands and moves the dial?

I have a Racetech one on my zetec, I'm sure its the oil pressure pushing against a spring and the deflection shows on the gauge. Its instantaneous when the engine starts so no heating of bulbs or anything i can see.

wouldn't the temp vary with oil pressure then? or is it taken from somewhere with where its not pressureised? like in the sump?

either way it didn't work so i cut the wire/tube thing and ripped it out, just couldn't work it out, the sender part is quite a big ish thing, and it's in a non pressureised area, and when i cut the wire thing right at the sensor oil didn't get out

No chance of it working now !