Choosing A Radiator  
I've gotten quite a few emails concerning which would be a better radiator or oil cooler. Hopefully this will help clear things up...

The main concern when choosing a radiator or oil cooler is the material that it's made from. Switching from a radiator with plastic or nylon tanks to an all metal unit would be benefitial in that its lifespan is far greater then the plastic/metal unit. However, if a unit is made from a metal with a lower thermal conductivity coefficient, then the cooling ability will suffer. A material's thermal conductivity coefficient is how well a unit conducts heat. The higher the coefficient, the better it will be at cooling the engine coolant, oil, or transaxle fluid.

The following are a few different metals along with their thermal conductivity coefficient at a given temperature...

Silver 409
Copper 386
Aluminum 212
Magnesium 154
Brass 120
Lead Solder 34

An aluminum radiator would normally be better at conducting heat then a brass radiator. If a radiator is constructed completely of aluminum and the fins are attached using lead solder, then the radiator's ability to conduct heat will be severely handicapped since the heat will need to conduct through the lead before it reaches the fins. Putting the value of the metals aside, silver would be the best material to make a radiator out of considering thermal conductivity.

Another consideration besides thermal conductivity would be weight. The following are the same metals listed with their atomic weights...

Lead Solder 207.2
Silver 107.9
Brass 64.1
Copper 63.5
Aluminum 27.0
Magnesium 24.3

If you were to make a radiator out of silver, it would conduct heat quite well, but would weigh almost twice as much as a brass or copper radiator, and four times as much as an aluminum radiator. The only real considerations would be copper or aluminum. Copper weighs about 2.4 times more then aluminum, yet conducts heat 1.8 times better. If you're looking for the lightest radiator to keep the weight off your car, aluminum would be the best choice. If you're looking for a better cooling radiator without concern for weight, copper would be the one.

Finally, if you're looking for the overall best radiator or oil cooler, you could simply divide the metal's thermal conductivity by it's weight to get the conductivity to weight value.

Aluminum 7.8
Magnesium 6.4
Copper 6.1
Silver 3.8
Brass 1.9
Lead 0.2

Figuring thermal conductivity to weight, aluminum would be far better then copper would be. Magnesium wouldn't be a consideration due to it's poor strength. At equal construction quality, aluminum would be the best choice for a radiator or oil cooler.

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