Here's Proof You Should Absolutely Pre-Fill Your Engine's Oil Filter
Scientific testing by a certified oil specialist shows why you should always pre-lube your engine oil filter to ensure your engine's good health.
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- Thread starter woxofswa
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Difficult to do ( fully, anyway) with a standard horizontally mounted filter, but doing an initial crank with no priming and mixture at cutoff, until you see oil pressure helps a lot to mitigate dry starts.Here's Proof You Should Absolutely Pre-Fill Your Engine's Oil Filter
Scientific testing by a certified oil specialist shows why you should always pre-lube your engine oil filter to ensure your engine's good health.www-motor1-com.cdn.ampproject.org
FireMedic_2009
Well Known Member
The difference is minuscule and not worth talking about. Unfortunately most of the filters are mounted sideways. I suppose it’s worth cranking the engine with the mixture off til you get pressure
I'm in the habit of changing oil on a warm engine (which means freshly lubed) and then as soon as I'm done I crank it up and idle it for 20-30 seconds to build pressure in the system and shutdown, check for leaks etc before recowling. I figure a dry-start is somewhat mitigated by the fact that the engine was running just an hour ago and can't be completely dry in the first place.
From the article - "Most engine oil pumps get oil directly from the filter, so to prove why pre-filling is so important, Speed Jr. set up an oil pressure gauge to show what would happen if the engine ran with a dry filter. Priming the engine (spinning it without adding fuel or spark) reveals that the engine would run for a couple of seconds with no oil pressure at all, as there's no oil to take from the filter."
Lycomings and, I believe, Continentals have the pump between the prescreen and the filter so this is not true for our engines. I was under the impression all automotive engines are likewise - otherwise there would be no reason to have a "burst pressure" rating on the oil filter as all oil filters would be operating at a slight vacuum. What's the story here? Building oil pressure will absolutely happen faster with a prefilled filter - but not because the oil pump is starving for oil.
From the article - "Most engine oil pumps get oil directly from the filter, so to prove why pre-filling is so important, Speed Jr. set up an oil pressure gauge to show what would happen if the engine ran with a dry filter. Priming the engine (spinning it without adding fuel or spark) reveals that the engine would run for a couple of seconds with no oil pressure at all, as there's no oil to take from the filter."
Lycomings and, I believe, Continentals have the pump between the prescreen and the filter so this is not true for our engines. I was under the impression all automotive engines are likewise - otherwise there would be no reason to have a "burst pressure" rating on the oil filter as all oil filters would be operating at a slight vacuum. What's the story here? Building oil pressure will absolutely happen faster with a prefilled filter - but not because the oil pump is starving for oil.
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[email protected]
Well Known Member
I do not prefill the oil filter. Never have and won't be doing so in the future.
If the engine has been ran in the near future it has oil in all the parts it needs to be. The term starting an engine DRY is bunk. Oil doesn't just disappear from the bearings. An engine will run for quite a long time (at least a minute or so) before having any problems.
Ya, about burst pressure. You wouldn't need any burst pressure if the oil was sucked through the oil filter. Really???
I do agree the engine has no oil pressure for a few seconds though.
As a mechanic for the last 55 years or so I have made a mistake or two.
Changed the oil on a car and forgot to put the drain plug in. Added all the needed oil, But, it went on the ground under the car. MUST HAVE BEEN DAY DREAMING
Proceeded to start the car, backed it out of the service bay, drove it out onto the street before I noticed the oil pressure was ZERO (no light). Drove it back to the bay to see the problem OOOPPPSSSS !!!! no oil, Put plug back in added oil needed and started it up. Worried Worried about damage. That particular car was in service for at least the next 60,000 mile that I knew of....
Had a race motor blow the filter gasket out more than a quarter mile from the pit. Driver drove to the pit and we changed the motor, Because we thought it would be toast running at 7,000 RPM. NOT TRUE.
After tear down I found everything looked like new. NO damage anywhere. WE actually put it back together with same bearings, rings and just new gaskets. Ran fine and never blew up like we were afraid of.
I could tell more stories but you get my drift. Then again maybe I'm stupid for not doing so.
BUT my luck varies FIXIT
Desert Rat
Well Known Member
If you look at the oil system diagram for a typical Lycoming 4 banger, it sucks oil through the sump screen into the oil pump, and is then under positive pressure pushing oil through either the cooler or vernatherm (whichever has the least resistance), into the filter, then on into the galleys etc. Pretty much everything is downstream of the positive displacement pump. Unlike what's being referenced in the attached article, there isn't really anything sucking air. Instead, there's wholesome slick dino juice shoving air out of the way.
I guess it can't hurt anything to pre-fill the oil filter, but I'm of the opinion that it doesn't really do any good either. The relatively small amount of air in there is encouraged to move along pretty quick at 90 psi.
As far as draining the cooler, I believe this does more harm that good unless he fills it up again. It' true that my big cooler and the lines going to/from it do hold close to a quart of oil. But even with the oil cold and the vernatherm open, if the cooler is empty it seems like the path of least resistance is for the oil to want to fill up the oil cooler first. i.e. there's a reason Lycoming tells you to fill up the oil cooler on a new installation before you crank it with the plugs out.
I guess it can't hurt anything to pre-fill the oil filter, but I'm of the opinion that it doesn't really do any good either. The relatively small amount of air in there is encouraged to move along pretty quick at 90 psi.
As far as draining the cooler, I believe this does more harm that good unless he fills it up again. It' true that my big cooler and the lines going to/from it do hold close to a quart of oil. But even with the oil cold and the vernatherm open, if the cooler is empty it seems like the path of least resistance is for the oil to want to fill up the oil cooler first. i.e. there's a reason Lycoming tells you to fill up the oil cooler on a new installation before you crank it with the plugs out.
There is risk of introducing foreign material into the filtered (clean) side of the element.
