The drain plug is in the radiator. You're putting it in your radiator?
??? tomato tomotto???
Maybe you're splitting hairs on what we call it but I know of two drain plugs for the coolant system. One on the radiator also known as the petcock, and one for the block's water jacket under the 4th exhaust port.
For the small cost of buying and running it, it would be well worthwhile just for getting heat sooner. Whether it directly helps FE, or just makes me more comfortable and relaxed (and less likely to drive for faster warm-up instead of hypermiling)...I want one!