Forum Discussion

Jayco-noslide's avatar
Sep 19, 2014

Generator fuel consumption?

We have a 2003 Itasca Class C with a 4000 Onan generator. Does anyone know how much fuel this consumes? When I had a Honda portable I could tell because I filled the little tank but no way to know with an onboard. I think it ran 5,6 hours or more on less than a gallon so I assume this 4000 onan uses at least twice that much fuel?

4 Replies

  • Note that a 4000 watt 60Hz Onan, from the chart above, consumes about 0.3 Gal/hr with no load, and about 0.5 Gal/hr at one-half load.

    Our Itasca RV is only a 24 footer, so it's air conditioner is a 13.5K BTU unit. I estimate that this air conditioner loads the Onan at about 40% when running steady - but air conditioners usually are not runnning constantly - at least the power-consuming compressor portion of RV air conditioners cycle ON and OFF. So ours is probably using 0.36 to 0.38 Gal/hr when powering our 13.5K air conditioner in all but the very hottest and humid conditions, during which it might be running non-stop and maybe consuming 0.40 to 0.45 Gal/hr. I use Mobil 1 EP and a special spark plug in our Onan in an attempt to help it maybe consume just a bit less Gal/hr and run just a bit cooler.

    FWIW as a side note, once we used BOTH the Onan-powered coach air conditioner and V10-powered Ford cab air conditioner in the Texas Panhandle during August for a fast coach cool-down after being outside rockhounding in order to avert heat stroke and have a comfortable lunch!
  • my book estimates at 50% load i should use approx. 3 hrs per gal.