I put a quart of oil in the tank every spring as a tonic to ensure the IP is adequately internally lubricated but as a regular thing I don't think its worth doing. The IP is lubricated by engine oil, the engines in the 115 (and I presume earlier) cars have an oil resevior you need to fill but later cars are lubed by oil from the engine.

Other engines don't have this feature and need additional lubrication.

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Sadly Benz-less