I bought a 1991 240sx last September 2004 because I was going to modify it for the street. The car was in good condition. Had over 150,000 miles on the original engine, but ran like a top. The car had a noticeable smoke problem and a good acquaintance of mine told me to get Lucas Heavy Duty Oil Stabilizer. It, without a doubt, was the best advice I have ever listened to. I changed the oil and added just one quart and WOW. The engine seems to have a new lease on life. The smoking is gone completely and the engine seems to perform better. I use the Lucas oil treatment every time I change my oil without fail. I also use it in my wifes 2000 Impreza RS. Not because she has a problem, but because I like it so much I figure it can only help. At work I have become the Lucas unofficial spokes person. I tell people whom I work with to buy your product. After they try it they thank me. This product is simply amazing. I highly recommend it to anyone who wants the best for their engine new or old. Thank you Lucas. Walt B.