Prefilling Oil Filters - Necessary?

Messages
15,715
Location
N.H, U.S.A.
On horizontal filter I put in enough to wet the media.
That alone should get the flow going faster.
I would say it would make it HARDER as it is an obstruction along the way to the oil pump to evacuate air,
Think of water hammer. Unless you could fill the drill all the way back to the Pump.

I used to prefill. when I had VVT rattle after oil change.
It Didn't do anything that I could tell.

Then, For a while I half filled them. So the pump could push the air column out quickly, without a slug of oil travelling at
high speed like a bullet, then whacking into who knows what inside the engine.

On the new Subaru series it doesn't matter as the car starts DRY every time after a hot cool-down.
Every time.

Somehow its still running. But not quietly. I don't think the stationary HLA are as happy as they once were.
But at least you don't have to adjust them. Just tear the whole engine apart to replace them at great cost.
What progress!
 

Strokenmerc

Site Donor 2021
Messages
191
Location
Va
I have always prefilled but I would bet hunderds of thousands of filters are screwed on at fast-lube places empty every year. Can't imagine it makes much difference but I prefer to minimize the time without flow at start-up.
 
Messages
26,510
Location
PNW
Then, For a while I half filled them. So the pump could push the air column out quickly, without a slug of oil travelling at
high speed like a bullet, then whacking into who knows what inside the engine.
If a slug of oil hitting parts was detrimental, you'd see damaged engines all over the place because the majority of oil changes do no involve pre-filling the oil filter.
 

gathermewool

Site Donor
Messages
8,781
Location
New England
I just pre-filled the upside-down filter on my Subie and it went well. I filled it to the brim and let the media soak up as much as possible, which was all but a little in the bottom of the center hole. I then rotated the filter horizontally to distribute the oil and installed it. Not a drop was a lost.
 
Messages
1,340
Location
south dakota
I do not pre-fill because I always worry about spilling oil. If I had a hoist where I could stand underneath my vehicles it would make pre-filling easy. The Jeep is impossible to pre-fill and my F-150 has a sideways filter. The Honda is kind of difficult to pre-fill as well. My Corvette could be pre-filled however its so low to the ground and not worth even trying. I was at a car show one time and they had a car that was run without oil wide open until it quit. People could buy tickets and write down how many minutes and seconds before it would quit. The engine about 10 minutes before it finally seized. It was run without any oil in it. I believe the layer of film on the oil is enough to protect the engine for a couple of seconds. I believe a flooded engine is much harder on initial startup than running with an empty filer after a new oil change. The trick is keep decent OCI intervals and maintain your vehicle if you want it to last a long time.
 
Messages
15,715
Location
N.H, U.S.A.
If a slug of oil hitting parts was detrimental, you'd see damaged engines all over the place because the majority of oil changes do no involve pre-filling the oil filter.
There will be no slug of oil - compressed by an air column - with a filter that was NOT pre-filled.
My exact point.

Thank you :)

Again do a partial fill on larger filters - but not all the way - unless you can also pre- fill the drill down to the oil pump.
I do this on the FB subaru by pouring oil in the filter adapter outlet and the inlet, then quickly screwing on the filter.
Actually a waste of my time as these dry start every morning to to an empty inverted filter.
Another Stupid Subaru engine design.
Time they go to a "slant" I4 and get away from this garbage engine design.
 

gathermewool

Site Donor
Messages
8,781
Location
New England
There will be no slug of oil - compressed by an air column - with a filter that was NOT pre-filled.
My exact point.

Thank you :)

Again do a partial fill on larger filters - but not all the way - unless you can also pre- fill the drill down to the oil pump.
I do this on the FB subaru by pouring oil in the filter adapter outlet and the inlet, then quickly screwing on the filter.
Actually a waste of my time as these dry start every morning to to an empty inverted filter.
Another Stupid Subaru engine design.
Time they go to a "slant" I4 and get away from this garbage engine design.

Shirley you jest.
 
Messages
15,715
Location
N.H, U.S.A.
Shirley you jest.
shirley.jpg
 
Messages
833
Location
South Carolina
I always prefill the 2 qt filter on my Silverado ;)
I never pre fill the little 7317 filter for my Honda but if I had a 2 qt filter I would consider it. However, as mentioned earlier the oil film is probably more than sufficient during the 2-3 sec it takes for the pump to fill the filter and other areas.
 
Messages
372
Location
Scottsdale, AZ
I never do it, all our cars have sideways filters so it would be a messy faff and there is plenty of oil inside the engine so I’d never worry about a dry start. I could see the benefit on large class 8 semi trucks where you’re putting like 15 gallons of oil in and the filters are enormous and can take a couple of gallons each.
 
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