I went with the Delo 400 upon purchasing my '85 300D and ended up having to replace the "o" rings on the oil return line from the air filter housing to the oil pan and while I was in there I replaced the "o" rings and gaskets on the return line from the turbo. At 225k miles I have absolutely no oil leaks and I do not use enough to matter betweent the 3k mile oil changes. I will say too, that I have had to replace ALOT of the rubber components under the hood - especially the ones that had been exposed to any oil.

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Jim