Any harm done if leaving engine oil & trans oil out

As long as you keep the moisture out, I would think several months would be OK. I've had no ill effects with engines out for several months with no oil in them. If you do put oil in it, the oil lays in the crankcase and doesn't do anything else. So in the end, it doesn't make much difference. This is just my opinion. I'm sure there's a few engineers on the list that will give you chapter and verse on how long it takes for aluminum to start corrording.

Bob Wassam

 

I guess I am not sure of your time interval. Are you talking weeks, months, or years??? Is it going to be in the house, or in a unheated area near a cement floor??

Oil does dry up over time, but temperture swings seem to speed up the process along with cycles of high humidity/low humidity, especially if its enough to create condensation. I once left a motor under a work bench all winter in a garage that I only heated when I worked out there. In the spring I removed almost a gallon of water from the crankcase.

If your just concerned about short time, its not a big deal. Anything approaching a year or more should be looked at differently. There are special plugs that replace spark plugs filled with dessicant, used to be called protex plugs. If they change color you know moisture is present. Fog all the cylinders with oil, fogging spray, fuel oil, something good. Fog inside the crankcase. Get those paper towels out of there, could cause more harm than good. Then seal up every opening after spraying liberally with fogging spray, or oil. And we mean every opening. Also, smear a good coat of heavy grease on any exposed areas of machined steel, such as the crankshaft or flywheel. Then store it away in a warm dry place and you will be okay for potentially decades. At that point, mice or other vermine will be a greater threat. Rodent urine is highley corrosive to aluminum.

On start up, your biggest issue may be oil pressure. You will want to crank the motor without ignition until oil pressure registers before attempting to start the car. Have fun. If you also crank it without plugs, it will blow out any oil in the cylinders. And dont forget to wipe off all that grease