thank-you for the help
I found this video
click here
The guy in the video recommends lithium. He said motor oil attracts dirt and WD 40 removes the lubricant. They both have their purpose but it doesn't sound like their best purpose is garage door lubrication.
In the video it mentions a powder coated spring not requiring any lubricant. My house was built 2 years ago---do you think they all have powder coated springs?