I would only use wire approved for auto use Mike. The automotive use wire has specifically specified insulation.

Probably not.  Most extension cords are made from 16-14 gauge stranded wire, but its not the same as what's meant for automotive use.  Its designed to carry high voltage at low amperage.  Typically those cords are maxed at 15 amps.  I buy heavy gauge cords for business use or else the high amp draw on the thin cords can trip breakers, GFCIs, etc.

I use nothing but GXL insulated automotive primary wire.  It's resistant to all the fluids and is good for 256 degrees F, reasonably priced, and available in over a dozen colors from 18 to 8 or 6 gauge. But you knew you would get these answers...didn't you Mike? 
Also, I don't use any of the Auto Zoo, OReilly's crap.  Just the thought of solder makes the insulation crawl about an inch away.

 

Zip cord (lamp cord) is usually 16 AWG but does come in 14 AWG too.  You can cut off a short chunk and take it to your local hardware store to compare with what they have to get a better answer.  It would be OK for temporary wiring away from heat, corrosive/active fluids and abrasion.

The other stuff in the green sheath is probably 14 AWG and it could be a bit more durable than the zip cord if it's outdoor rated, but I'm not sure I'd use it in a car either. 

Probably not that important for cars but back when I built my plane I used a Mil  spec wire that had the individual wire strands tinned to prevent the dreaded “black corrosion syndrome” that we have all seen in 50 year old wires.
I guess that back in the sixties no one ever dreamed we would have to contend with wire issues in 2020.