I have used it for years and it's good stuff. I wouldn't say it eliminates all smoking though. I do find it keeps things cleaner and definitely boosts the cetane a bit. I thinks others have had more or less the same results with competitive products.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold