My J30 started riding rough and shaking a great deal during idle one day. Tryed everything, ignition coil, other brands of fuel treatment, nothing seemed to do the trick. Finally another J30 owner told me about the Lucas " Tune-up " in a bottle. I tried it on 3/4 of a tank of premium and what do you know, it worked. Now I use it in all of my cars. A bottle every three-thousand miles....Thanks Lucas for saving me $1,000 at the dealership. You bought a customer for life.