On our third class c with v-10, 2002, 2003 & 2005 chassis and never had oil usage like you are reporting or any engine problems, I use 5/30 regular oil.  Current 2005 chassis is right at 70K.   My usage is more like samsantdog reported.  You Don’t say what year and mileage you have.   If it is new you may need to follow your maintenance schedule to protect your  warranty.  Most new vehicles have now gone to around 7K for oil changes.   On our new car even though the manual says 7.5K or 7.5 months I keep getting notices from the dealer at 3.5K, which I ignore.   Regards, Dick