Marty, this is from the ONAN website:
<span class="ev_code_RED">Observe fuel recommendations for warm-weather travel:
Gasoline Generators - Use a good grade of regular unleaded gasoline.
Ethanol Blend - Not more than 10% ethanol.
Methanol Blend - Not more than 5% methanol with solvents and corrosion inhibitors.
LPG Generators - Use clean, HD-5 grade liquid propane gas in a mixture of at least 90% propane.
Diesel Generators - Use No. 2 diesel fuel with a minimum Cetane number of 45.</span>
Operating Genset in Hot Weather
Good Luck - Glenn