As far as I know its always been run on straight diesel fuel. That was one of the reasons I bought this car, there were plenty problematic "veggi oil" conversion on CL I wanted to avoid. The engine consumers less than 1/2 a quart between oil changes a lot of which is an oil leak at the vac pump I still need to fix. The #14 head has never been removed so I guess its just 193,000 miles of blow by and EGR that nobody ever cleaned.

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CENSORED due to not family friendly words