Almost any of the silver solders would be OK, the higher the silver content, the lower the heat to melt it (630C - 780C). The higher the silver content, the higher the price. You will need a silver solder flux.
Just be careful to apply enough heat and not so much as to melt the brass "nipple" or other fitting and of course do not try to do it in situ and set fire to the car.
However as others have said, there are plenty of cars going around with soft soldered joints - the secret to a good joint is clean the surfaces with an abrasive paper / wire wool, use flux and the right amount of heat to make the solder flow.
Ps: 3/16 tube is a bit small ??
Just be careful to apply enough heat and not so much as to melt the brass "nipple" or other fitting and of course do not try to do it in situ and set fire to the car.
However as others have said, there are plenty of cars going around with soft soldered joints - the secret to a good joint is clean the surfaces with an abrasive paper / wire wool, use flux and the right amount of heat to make the solder flow.
Ps: 3/16 tube is a bit small ??