When you test drive a new vehicle, you don't typically need to focus too much on how the vehicle runs. After all, it should be in pristine condition. This allows you to spend more of the test drive assessing comfort, handling, and other areas. However, when you're test driving used cars, you'll want to pay careful attention to a variety of specific things. Although used cars being sold by reputable dealers should have gone through an extensive inspection to ensure that they're in proper running order, it's part of your due diligence to watch for any concerns. Here are some specific things you should pay attention to.
Used cars can vibrate for a variety of reasons; something could be loose in the front end, for example. You may notice certain vibrations when you're driving along at highway speed, but pay special attention to how the car feels when you're decelerating and turning. Given that the weight transfers to the front of the car as you apply the brakes, this is a time that a front-end vibration will be noticeable. You may be able to feel a vibration in your seat or even in the steering wheel. If so, you'll want to bring this issue to the saleperson's attention so that it can be corrected before you purchase the car.
If the used car is from a relatively recent model year, its suspension is likely in good shape. However, if the vehicle is older, you'll want to pay attention to the suspension. Notice how the car responds when you drive over a bump. You want the impact of the bump to be nicely absorbed, but not have the car feeling as though it's riding up and down like a boat on the ocean. Similarly, you shouldn't hear any creaking in the suspension as the car navigates over bumps.
You also want to ensure that the used car doesn't pull to either side. This can indicate an alignment issue with the front end, which is something that you'll want to get fixed before you negotiate your purchase of the car. When you're driving on a straight road, notice if you have to apply pressure to the wheel to keep the vehicle in your lane. For example, if the alignment is off, the car may drift to the right a little, prompting you to apply a little leftward pressure.