It's funny or not (depends on the person who is asking) that your basic ICE (internal combustion engine) with spark plugs, starter motor, radio, GPS, alternator, LIGHTS and more has folk that won't use a cell phone won't give an old car any thought about this.

Way back when we were doing radio emission tests a car would drive by and we'd have to pause until it left the valley we were in.

It depends on the car but most emit a lot of EM noise. As to what's slightly better, think diesel.

Good question.