bah humbug. No-one calls a combustion engine a motor, not in the UK at least. A more accurate description of the "thing" that makes your car go...

engine [Show phonetics]
noun [C]
1 a machine that uses the energy from liquid fuel or steam to produce movement:
a jet engine
a car engine
My car's been having engine trouble recently.

Don't get me started on "gas" unless your car runs on gaseous form (ie gas oxygen, methane) then the stuff used in cars is not gas, well only the stuff that evapourates.