For something as simple as swapping your chain for race day, you can save an easy 2-6 watts (at 250 watt power) vs your current oiled chain, and this friction saving figure just goes up and up at higher watts output.
A lot of cool friction saving information is detailed on this site, but the quick wrap is that your chain is the hardest working drivetrain component by far (think approximately 20,000 link articulations per minute at 90 cadence on the big chain ring). Oil quickly becomes a grinding paste, and an oiled chain quickly becomes a friction monster. Most especially the chain you use all the time in training that you were also thinking of racing on.
This is why a race chain delivers far more friction savings than what you can (or have) achieved by upgrading all of the bearings on your bike combined. And swapping a chain is very simple, if you haven’t done it before, don’t worry it’s much easier and quicker than you think, and we are here to help.