912- Getting oil back into circuit/filter after oil change

So I have a question as a relatively new 912ULS owner.  And I'll preface this by saying I have done exactly one oil change and I didn't do what I'm about to ask, I just wondered as I was counting prop rotations by hand (and I do essentially what I'm about to ask with a motorcycle that has sat all winter to get oil flowing prior to start):

Would there be a significant difference between rotating the prop by hand versus leaving the mags off and cranking it with the starter, watching it rotate approximately 20 times? 

Hi R-O,

Just for conversation:

I would advise caution, when checking the oil level; When I "burp" my ULS cold, I usually get about 1/2-3/4 full on the dipstick.

If a wait, say 10-20 minutes, and repeat the procedure, the oil level comes up to full.

On the first reading of dipstick, I may have been tempted to add oil. This would have put the engine oil content well above the recommended system quantity.

This may then have resulted in excess oil being expelled/blown overboard ie a waste of oil & messy airframe.

I am not advocating always allowing sufficient time to elapse for remaining oil to drain down to the crankcase exit point, before being sent to the oil tank but that pilots should get to know what constitutes an acceptable oil level, for their installation, knowing that more oil remains in the crankcase.

On oil changing/refilling - the above observation (oil still in crankcase)  should also be considered when refilling.

Do it by hand. We rotate the prop for two reasons and not just to check oil level. First we want to check for hydra lock. It's not real prevalent, but it does happen. I saw a Sting aircraft do it 3 months ago. Hydra lock is oil in a cylinder that won't let it rotate and will slam the engine to sudden stop if you just try and start it. This usually happens with some older aircraft and equipment. Things like mounting the oil canister too high like KitFox used to do and some of the older oil filters didn't help. The second thing we check is the oil level and each engine is kind of its own personality here. Some rotate a prop 3-4 times and it gurgles and some have to do it 20 times. Then sometimes depending on things like outside air temp (cold weather) the level on the dip stick isn't 100%. That's no big deal so don't get hung up on that.

So if you rotate the prop with the engine starter system and you have oil in a cylinder (hydra Lock) then you will instantly damage your engine when it SLAMS to a stop.

Turn it by hand for a few turns. Plus using the engine starter to do this will just add wear and tear on the starting system.

Good response Roger