C172 pilot reported impacting a vehicle during taxi out from the ramp area.

Narrative

I flew a Cessna 172 from the ZZZ1 to ZZZ to pick up another pilot and return to ZZZ1. Arriving at ZZZ; the apron was crowded with planes including one at both fuel pumps. I taxied to the back of the apron towards the hangars to the only clear space to park the plane. I shut down the engine; got out and located the other pilot. We got in the airplane and I went through the startup portion of the standard checklist; but I did not perform a walk-around.The apron was still crowded and there was a taxiway directly in front of me that made a left turn up ahead and joined the main taxiway and on to the runway. I said to the other pilot; 'Let's just taxi straight ahead.' I no sooner started moving when the plane jerked to the right. We got out and saw that someone had parked an SUV car between the hangar and the taxiway with the rear hatch door up. The leading edge of the wing had contacted the upper edge of the hatch door making a short crease in the outer end leading edge. There was no damage to the car door at all. We could not locate the owner of the car.There was no effect or any distortion of the upper and lower parts of the wing; the plane seemed airworthy so we returned to the home airport. The return flight was uneventful; the plane performed normally.In the future I would always make a walk-around even if on the ground for a short time. Also; in crowded airport conditions; look ahead from outside the plane for any obstructions in the direction I would be taxiing.