On a new Generator change the Oil after the first 20 hours. Reference the Hour Meter at the Start/Stop Switch.
Change the Oil and Air Filter every 150 hrs thereafter. The MicroQuite holds 1.6 qts of Oil. The Oil Drain is in the middle, on the bottom side. Above freezing, 30 weight oil is recommended. There is not an Oil Filter on the MicroQuite.
Spark arrester or muffler. Clean every 50 hours. Remove 2 plugs, start engine and run for 5 min. and any debris will be blown out. Replace the plugs once it's cooled down.
Replace the Spark Plug, Fuel Filter every 450 hrs. In an emergency, use a dime to check the spark plug gap.
Adjust Valve Lash and Clean or Replace Cylinder Head every 450 hrs, by an Onan service center.
The Onan 4000 MicroQuite has no Oil Filter. It uses an 1/8 of an ounce of oil per hour as part of the cooling process, so check the oil at least every 8 hours.
There is an altitude adjustment on the Carburetor. Power from the Generator decreases as altitude increases. It maybe necessary to run fewer appliances (at the same time) at higher altitudes.
There is NOT a Low Oil Shut off or a High Temp. Shut Off, unless you know for a fact these features are on your unit.
If you notice oil in the air cleaner (breather) housing, this might be caused from Blow By from the OHV that feeds back to the Air Cleaner through a hose. You can pull the OHV cover that has about 7 screws in it and replace the breather valve and gasket. Onan Reed Valve # 123-1920 - Gasket # 110-3860