It's very common, mine does generally short journeys, 8 miles each way daily and it was pretty bad before it got serviced, regularly check it now and seems fine. As long as your not using lopads of oil/water, there are no miss fires or smoke coming out of the zorst it'll be ok and an oil change will sort it. I would however be a little wary if its a car your buying so get them to pressure test it and if its ok and they give you a decent warranty cant see any problem.