What gauge wire should I use when installing oil pressure,tranny temp,water temp gauges ?

 

18 gauge would be sufficient as there is no major current involved. You could use smaller if you have it.
Randy

 

Im assuming these are mechanical(analog) gauges. The oil pressure has a line for the oil pressure, tranny temp and water temp should have their own wire from the sender to the gauge already if its a mechanical gauge. If they've been cut, the gauge will no longer work.

However, if its a electric gauge, you just need to hook up power, and illumination. Those wires dont need to be very big. If you have wires that were removed from a vehicle (i know i do from some ive stripped), any wire will do just fine for your purpose, but remember, if your not sure, go a little bigger gauge than you think u need. Bigger is always safer, never smaller. In your case, any wire from a vehicle will do just fine.