My guess would be better, since propane burns quite a bit cleaner, reducing the amount of pollutants in the engine oil. I would imagine that propane also has fewer additives/modifiers than gasoline, also aiding in reducing the amount of pollutants in the intake and combustion chamber.

Propane, although having fewer Btu's than gasoline, does have a higher octane rating - so pre-ignition (and its adverse effects) ought to be greatly reduced/eliminated as well.

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D