1) i don't run my oil 3.3 times longer than i should.
2)So the oil is cleaner-BFD,if you're taking proper care of your vehicle,you should be changing it at regular intervals anyways,so the point is moot.
3) I just passed a gas station with 87 octane at 2.99 a gallon,so there goes the "it's cheaper thing".
4)This propane thing is not a new idea by any means.Having said that-if it's such a bitchin' idea where are they all?
Propane conversions do have their place:
Indoor Forklift and other vehicles
Ranch vehicles
Tugs(Airport type)