hbdunn

I believe Jake and Charles recommend not prefilling, which I have never done. Lake claims in his Porsche engine there was no bearing material after prefilled and that previous changes without prefill there was. Starts talking about this at 6:30.

Icelia

Bullshlt... The filter is full every time you start the car. The oil is perfectly clean out of the bottle. Certainly cleaner than it is at 5k miles. I don't have to watch a video to know that what I have been doing for 25 years and hundreds of oil changes (pre-filling the filter) is the right way. Not going to waste my time on this pointless question. Why am I wasting my time even answering?

zbomb

I have pre filled my filters on every oil change it was possible to do so since I was a kid. The M96 when the spin on adapter went on, the dry sump system in the car now, all the families various DD's... all of them.

Brad, maybe you could do an experiment and log the time it takes to build oil pressure after an oil change with both a pre filled filter and non pre filled and see what it says.

Icelia

There is a drainback valve built into good filters precisely so you DON'T have an empty filter when you start the car each time.



"And here is the big thing. Most filters these days have check valves in them, and the primary one is an anti-drain back valve. That anti-drain back valve prevents the oil from being syphoned out of the filter when the engine is shut off. Now when that happens the car, the engine starts with no oil, because the oil pump has to fill the filter, then the oil circulates to the moving parts of the engine and that can add years of damage in just a single start. "

Quote from this article:
https://motorweek.org/goss_garage/oi...%20shut%20off.

hbdunn

My point is that experts here have said not to prefill. And why so hostile?

https://rennlist.com/forums/996-foru...l#post19009509

Originally Posted by KentBigDog
@Charles Navarro Why do you recommend not prefilling the oil filter with the spin-on? I've always filled my oil filters to reduce the amount of time the motor is without oil pumping through the engine.



We have seen several instances where the oil system ends up with an air lock and the engine won't have any oil pressure. Jake recommend against pre-filling any oil filter.

There are plenty of engines with filters that go on upside down or sideways that cannot physically be pre-filled, so installing a dry filter on your engine won't cause any issues.

silver_tt

Discussed here last weekend:
https://rennlist.com/forums/996-foru...l#post19093002

Oil is the cleanest it will ever be out of the bottle, I have no idea what Lake is referring to when he says some people think it's dirty.

I think you're overconfident in your response. There are many engines that it is not possible to pre-fill the oil filter because it's mounted horizontally or inverted. Try pre-filling a Mezger and let me know how it turns out for you.........

Mike Murphy

Something to note: A cold start on an M96 engine has a DME timer that decides what RPM target should be hit immediately after starting the engine. The longer your car sits, the higher the RPM target. On my ‘99, if it sit for over a week, I can easily hit 2,000-2,500 RPM. I remember reading somewhere, but cannot find it, this has to do with the oil pump design. The oil pump design is such that it can have trouble priming or pumping unless its internals are moving fast enough. Maybe it’s because the pump sits higher above the oil level, or maybe there’s another reason.

This is one reason why some also don’t recommending pulling the fuse that operate spark, and turning the engine over for many seconds to prime the engine with oil after major service work or a rebuild: the starter cannot turnover the engine fast enough to prime the system. Only a big spike in RPMs can do this.

So what is often good advice in general, and I think pre-filling is good advice generally, it may not be suitable in every case.

Porschetech3

Yep, Porsche , me , Jake ,Charles , all recommend not to "pre-fill" the oil filter on a new or rebuilt engine where there is no oil in any of the oil galleys, the oil cooler, the oil pump, the heads, lifter cradle ect..it is all just a bunch of air pockets..... This is the most important scenario where having a slight " liquid block" in the middle of the system can delay pressure /flow build-up......The best procedure is to start the engine then shut it down 2-3 times, then leave it running..

Or if you want to do it the sure fire best way, then put the required oil in a pressurized container and pump it into the oil system at 100 psi.....( stock cartridge filter,,not one with a drain-back check valve)

Sure the other scenarios pre-filling the oil filter can be slightly more beneficial then not pre-filling, but you will find no such recommendation in the Porsche service manual.....And as people are creatures of habit who always want to do it one way or the other at all times....

sanyata

Although the Mezger is a dry sump engine, it does have a sump, with a drain plug, that holds some oil. Some folks will pour 1/2 a quart of oil into the sump before installing the new filter. So, in a way, that's pre-filling the system to cut down on the semi-dry running time.

996-CAB

I think there is something funny going on iwit this argument for or against the prefill. The dirty oil claim is nonsense, It is fresh oil.
Here is the setup: I change the oil and filter in my car every 1,000 miles. (gives me something to do, can't hurt and is super easy). My car goes into professional storage this time of year and I only had a couple hundred miles since the last change so I just changed the oil and did not change the filter, which would be like pre-filling it, wouldn't it? Car ran fine. Have LN spin-on and use the larger NAPA Gold 1258.

hbdunn

When you remove the filter you remove the oil past the filter. So you still have oil between between the filter and the top of the engine that will start lubrication immediately.

Edit: Tom said it better below.

tommelton

You say you changed the oil, and said you did not change the filter. So if you didn't REMOVE the filter, no, not same thing. Removing the filter allows the oil passages above the filter to drain back into your drain pan under the removed filter. The theory is the air between the sump and the changed/pre-filled new filter and the air after the new filled filter can cause lack of flow for an extended time, moreso than an empty filter as all that air on both sides of filled filter is compressible.

Icelia

Unless someone can show hard data that sufficient oil pressure is reached with an empty filter before a full filter, and that test is collaborated by a second person... I say it is pretentious smoke blowing.

So I challenge anyone to show hard data.

Should be easy. Real time pressure monitoring at the same time as an RPM graph. Time in 100ths of a second until oil pressure reaches say 30psi will definitively answer the question.

(if your argument is based on not filtering the fresh oil, then filling the outer holes and allowing the filter to gravity filter solves that problem)

Unless you are willing to do, or have done this test; how is what you say anything more than an opinion?

wildbilly32

Dude who reconstructed my engine said "Do NOT prefill the oil filter."

Good enough for me.

yaz996

And he explained the "why" pretty clearly to me after I spun a rod bearing 70 miles into a new engine build.