Lugnut
I would avoid using the blue clamp on "splices" you have on your cigar lighter if at all possible.
I do a lot of marine wiring and would never use them. They almost always end up being too big or too small for the wire gauge, too big and it just cuts the wire strands, too small and it does not make a good connection. Pop the cover and just look at how the "connection" is made.
Butt connectors are the connection of choice, with the correct crimp.
Find a local West Marine or BoatUS store and look at the connectors they carry. Anchor is the brand and is at the top of the quality list.
They are available in 3 basic sizes, 18-22 gauge (red), 14-16 gauge (blue), and 10-12 gauge (yellow). You can also get them in "step down" sizes, 10/12 - 14/16, yellow with a blue stripe on one end and 14/16 - 18/22, blue with a red stripe on one end. Also available are the connectors with a heat shrink jacket, filled with a sealing adhesive.
Step down
http://www.boatus-store.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=20002&langId=-1&catalogId=20002&productId=39423The wire available at the marine stores is also superior to automotive grade. Typically the Anchor brand wire is more flexible, higher number count of smaller strands for a given wire gauge and it is silver tinned to resist corrosion.
Also available is a high quality adhesive lined shrink tubing in just about any size we would need, along with "Liquid" electrical tape.
Although I never used them, the posi lock connectors look pretty good too.