My wife owned a 1987 Buck Century with 140k miles on it with an oil leak that would dump about a quart every 3 weeks. She forgot to keep up with the leakage and let the car get about 2 quarts low. We were driving along on the highway and I noticed the engine getting a loud knocking sound and the oil light was flickering on and off. A good friend had given me a bottle of Lucas HD Oil Stabilizer to try and it sat in the trunk for 2 months. When we arrived home I was fed up with this car and put the Heavy Duty Oil Stabalizer into the engine. I Started up the car and within 2 minutes ALL engine knocks were gone, the engine shake completely disappeared, the oil light shut off and after a while the oil leak lessened. I've been a faithful Lucas Oil Advocate ever since. I just bought the Fuel Treatment for my 1997 Saturn SL and 2000 Toyota Tacoma and I can't wait to use it!!