Originally Posted by Shannow
More BITOG gold....
Facts
* new oil can be very very dirty
* prefilling put the new oil on the engine side of the rock trap
* bypass is closed when the filter is passing air to pre-fill the engine
* the dirty oil that you are emptying into the engine gets to go through the filter first before the bearings
* even at that point IF the filter is in bypass, then some/most of the oil gets through the media.
* prefilling gives you more chance of dropping something bigger down the hole, which another poster has identified with bits of foil.
* there is no metal to metal contact on that start, as there's plenty of oil and tribofilm left from when the engine was running.
Another fact is that I have never seen an automotive maintenance document produced by an OEM that tells one to prefill a filter...would be very interested in seeing one, to make it my first.
Of COURSE manuals telling you not to prefill are not common (the big diesel example cited excepted), as telling you to not to do something that you wouldn't normally do is superfluous:
* don't add coolant to windshield washer fluid
* don't use icepick to clear windscreen.
Maybe we should all make remote filter mount pump setups with screw on 2 micron hydraulic filters and pre-filter our oil before pouring it into the engine. Especially for Toyota's.
My question is why don't we see some crazy number in VOA's with metal counts, silica and insolubles if this were a problem? (Not being sarcastic, actually asking...)