OR! learn how to change your own tire...people it's really simple!
Although, if you were in the middle of changing your tire and "he" came up behind you...or work until 10 or 11...you might want to check out your surroundings or have a friend come and "stand guard."
Anywho--if the story is true...I would say a few things. If you have a weird feeling about a person DON'T TRUST THEM IF YOU DON'T KNOW THEM. If they feel safe, still be a little cautious. If they're in a suit and offering to change your tire....um just say no and say you'll wait for someone, come on, a suit?
Safety tips: 1) If it is dark out, park near a well-lit area. Preferably near a lot of people. 2) If it is dark, you DON'T need the exercise...park close to the building.