If you are monitoring car body vibrations, you need a good low frequency response. That means either a powered peizo accelerometer with a built-in amplifier or bare peizo accelerometer and separate charge amplifier. If you don't use a charge amplifier, you will lose most of your low frequencies. (Don't forget to set the scope input to DC, not AC). When looking for an accelerometer, try to get one with a low frequency response down to 1Hz or below. You can buy "DC" accelerometers with infinite low frequency response, but they tend to not have very good high frequency performance. You have to decide the range of frequencies you are interested in.