I'm just curious what this green light below the fuel gauge means. Are there any online guides for what the dashboard lights on a 3rd gen TL mean?

Another random question: were HID headlights standard on all 3rd gen TLs?

 

That just means you're cruise control is on and can be engaged if you want to set your speed. You can turn that green light off and on as well as set your speed with buttons on the right side of the steering wheel

 

I pretty sure they were, but don't quote me. I see you have a 07 or 08 so I know your car 100% has HIDs

 

Not yet, but the photo is of an 08 that I bought and am preparing to have shipped to me. Soon.

 

All TLs have had HID headlights standard since the 2nd gen.