I saw an out of county Ford Focus on I-24 just yesterday. It was burning so much oil there was a freakin' smoke screen coming out of the back of it. I don't really buy that new cars don't/can't have problems. Look man, registration tags in Hamilton are $25 plus the $10 emmisions testing fee. That's super reasonable. We don't have a wheel tax. I never really thought about exemptions for much older cars but I'll tell you this. If there is not a computer link on the auto they probe the tail pipe. They may have a different standard for older vehicles but every car is subject to emmissions in Hamilton. It may not be set up that way in your county.