I would run a zone fed copper pipe next to the oil supply line and use wire to hold them together and then wrap them in insulation.
Running a zone using 1/4 pipe is fine since that would just reduce the amount of water flow in that zone. (this assumes a single pump, parallel zone system)
FYI: I'm currently running my fuel oil furnace on diesel fuel since I ran out of heating oil. It's more expensive, however since my furnace is just a backup heat source it does not run very often.