If I switch a gas motor to propane, will the valves still be okay?

Factual Questions
1

A friend of mine recently bought a Honda generator and he is considering installing a kit (not from Honda) to allow it to run on propane. He is wondering if the valves will be okay under those conditions. His worry is as follows: leaded gas used to contribute to valve lubrication, but now modern engines don’t need the lead to do this… however, is there something else in unleaded gas that provides for valve lubrication, or is it all in the engine construction (induction hardened valve seats, etc.). He’s worried that if unleaded gas contains some sort of valve lubricant, not having it when he runs it on propane will shorten engine life.

Anyone?

2

From everything I’ve read running an engine on propane or natural gas significantly extends it’s life.

-Power output is slightly reduced, so there is less stress.

-Effective octane is very high, so the engine never suffers from detonation related stress.

-There is no liquid gasoline to wash the lubricating oil from the cylinder walls, so ring and cylinder wear is minimal.

-Combustion is usually very complete, so there is little carbon left in the cylinder, which is lightly abrasive.

-The complete combustion means that there is very little acid etc in the blowby, so the oil tends not to break down or otherwise get nasty.

3

Another vote for I heard that engine life is extended for the above reasons.