Are foreign auto electrical systems the same as US such that I can plug my U.S.-purchased GPS in a French rental car cigarette lighter receptacle without frying it; or will I need an adapter?
Worldwide cars electrical systems are the same. Don’t fret/worry.
Car and Driver magazine reviewed the Cadillac Catera in 1997. The Catera started out life as a German Opel Omega. The review mentioned the fact that the cigar lighter plug was the larger European model and an American plug was loose in the socket. Evidently there are two sizes, see: http://en.wikipedia.org/wiki/Cigar_lighter_receptacle
You may have to find an adaptor. And, of course, your GPS will need European maps downloaded to your GPS’s memory…
I believe the 12 volt automotive electrical system has been pretty much standardized throughout the world for some time now. You should not have to worry about frying your GPS unit.
You might want to make sure you can get the correct maps. The electrical connection should not be a problem.
12 volts is 12 volts the world over. Just remember the European 12 v. plug is slightly larger than the American version:(Wikipedia)
"12 volt cigar lighter receptacle and plug, size A
Receptacle inside diameter: 20.93 mm to 21.01 mm (median 20.97 mm)
Plug body diameter: 20.73 mm to 20.88 mm (median 20.805 mm)
Most often used in American automobiles.
12 volt cigar lighter receptacle and plug, size B
Receptacle inside diameter: 21.41 mm to 21.51 mm (median 21.455 mm)
Plug body diameter: 21.13 mm to 21.33 mm (median 21.18 mm)
Most often used in European automobiles, and sometimes as a second socket in American automobiles expressly for DC power connections."