I was skeptical at first, it's just an addition. Although I used the Liqui Moly engine additive and was very satisfied. I used this in our 2006 Taurus, which we call our universal cell phone. This is the 3rd car, it has not been used every day. 20 minutes after adding it, I noticed a big difference in switching. It no longer turns off on the first ride after a long period of inactivity. It's always been a good running car, now it's even better. That's why the Taurus was a good car for the fleet. Definitely recommend it.