Hi,
I have been using a drip system for years now, I mix all my old gas with my oil. I would not be afraid the mix 5 gallons of gas into a 55 gallon drum of motor oil.
If you are concerned, as the previous poster stated, mix a little less. ALSO, a drip system burns waste veggie oil real well too, I also cut that with motor oil, but i have burned straight veggie oil too