Your friend is fine with SCHaffers in all his farm equipment but not in his aircraft!You have to use an Ashless Dispercent oil. RPM's in a light civil aircraft do not vary enough to prevent the buildup ofmetalic ash based waste products that get burned in the engine. Because these engines are air cooled they are especialy lose when cold and oil consuption is quite high in aircraft IC engines! While this is not as big of a mistake as putting the wrong AV gas in it can still have very deadly results in the long term!