You see that little tag that says "For indoor use only?"
I may not be the brightest bulb on the tree, but cars are usually OUTSIDE.
1 little puddle, and your experiment is over.
You will need to hot glue every bulb base where the wires connect to water-proof them.
Turn this death trap off when pumping gas. You are not listening to what you are being told. You are only hearing what you want to hear.
Let me put it to you straight. You screw this up, they BURN. Burn = Fire. Fire + Pumping gas = a failed experiment because you are being cheap.
10 dollars in LEDs. 3 dollars in shrink wrap. A dollar or two in resistors, And some decent outdoor rated automotive wiring.
For under $20 You can use 5mm LEDs, much brighter, safer, and properly wired.
Take a few more minutes and you can use the car battery and a switch.
Its your car. Do it right.
Use the indoor Christmas lights for Christmas decor.
"Hey son, I just bought some Christmas lights!"
"Cool Mom, Im gonna hack them up and put them on my car!"