I think that if you need to use this stuff often to get a smooth start out of your diesel there are things that need to be replaced, like nozzles or maybe glow plugs. I did the diesel purge and changed the filters out on our old 300SDL and the start ups improved dramatically, this isn't a cold climate we're talkin here though and before i used it the idle would be shaky, it would smoke like all hell, etc. But after diesel purge the engine started as quickly and easily as my 300D with 617 motor. The 603 went back to ****ty starts after a month. I figure the nozzles on the injectors were crap, but I sold the car for $3000 instead of replacing them. Naturally I tried diesel purge on my 617 and it made no noticeable difference in the start up or power output.

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1985 CA 300D Turbo , 213K mi