28/030 is absolutely ample, delivers 17.5 amps continuous, and will go in blue connector, but don't use connectors solder and heat wrap then tape, otherwise moisture WILL get in.
It is easy to get the washers to seal, they go hard with age so just reanneal them by heating to cherry red with blow torch then drop in old oil, this will make them nice and soft again.
PLEASE DON'T HEAT UNDER THE CAR!!
tabetha