Petrol came first, as it was more obvious as a use of power than diesel because it was flammable and already in liquid form, yet diesel was discovered as a use of power for engines later. I would say petrol because when they invented cars they made petrol cars and from the chemicals etc. in petrol they invented diesel
When my dad was in the Navy, his friends used to use jet-fighter fuel to refill their Zippos, so I don't see why regular petrol should be any different. Just be very careful if you use petrol - do it outdoors, wipe the lighter after filling and wash your hands before lighting, as petrol is extremely volatile!