Last time (the only time) I did it, i splashed some oil over me and the driveway... then, i had to worry about the oil disposal, and haul old oil in the back of the car to the nearest AutoZone... all of that aggravation was not worth saving $20 - my time is more valuable, i'd rather pay somebody $20 for an hour of their work, instead of all the hassle i have to endure...

doing wires, installing cameras, mikes, charging circuits, on the other hand, is so much more fun!!!