Big Red Ferris06-25-2011, 05:47 PMi work for a company that installs Generac generators, the propane is vary reliable and clean power is lots stronger, motor will last longer, amsoil has a oil for the natural gas and propane units, remember gasoline is a liquid that cools in the motor, ur propane burns alot more btu's,a 990v twin is over 270,000btus full load 3600 rpm 2.5 gal per hr, so we tell cu