SuperBuickGuy

on the motors that are side mount - I put enough oil in them to get the filter element wet, then spin them on... far less mess. No, it doesn't fill, but the filter will have less restriction than dry (thus, less bypass oil in the motor).

and that's another reason to consider filling the filter. You poured oil in the top of the motor and wash whatever crud was in the top into the pan. When you fire the motor with a dry filter, the pressure to get oil through a dry filter raises - thus the oil bypasses the filter.... all that nice, crud-filled bottom oil from dumping in a gallon of oil in the top end...

and no, quickie filter places and dealerships don't - because they simply don't care whether or not your car blows up; you could never prove it was their fault that damage occurred from a dry start

Jud Chapin

In addition to filling the new filter with oil, I never start my cars after an oil change for at least a half hour. Actually, I'm not sure what this does but I do know that my oil pressure immediately goes to its normal range of around 40 psi. I think what happens is that oil pump becomes primed during this wait. I read this in a tech how to mag.

wheatpj

Never...would only consider priming oil filter if I had R&R'ed the oil pump.

wcsinx

2 problems here...

1. The small amount of air that moves through the oil train will not cause not a pressure increase (decrease actually) and will not open the bypass or at least no more oil readily than oil would

2. When your engine is running oil is constantly washing down from the heads back into the pan. You are not creating an unusual situation by pouring oil into a valve cover.

1. Your oil pump does not lose its prime during an oil change.

2. Oil follows the same laws of gravity as everything else.

Jud Chapin

Then why does oil pressure take more time to reach normal pressure when engine is started immediately following an oil change as opposed to waiting a half hour or so?

leadfoot4

I'll go out on a limb, and suggest that some of the 5 quarts of oil you just poured in, is still making its way down through the ends of the cylinder heads, through the lifter valley, and into the oil pan.

SuperBuickGuy

1 - it's your opinion

2 - it's the volume running down into the motor - just as a river is clean normally and brown during a flood, flooding the valley or the head with oil will wash crap into the oil pan.

wcsinx

Because you're imagining it.

Measure your results. I'll wait.

(I'm gonna guess you've never replaced an oil pump and had to reprime it)

wcsinx

1. Uhm, no, it's basic physics and fluid dynamics. The more viscous a fluid is the harder it is to pump. Fill the filter and your mouth with water, now blow through the filter, repeat with molasses ... which took more effort? Why do you think your pressure sender registers a higher pressure when you put a more viscous oil in it e.g 5w-30 v/s 10w-40? Air has an incredibly low viscosity in comparison to oil.

2. you're funny. Do you have any idea how much oil gets up there when the engine is running (not idling). Try this, take a valve cover off then drive to the grocery and back. Report your results here. Or maybe just watch this video


Scroll to the end (2:38 - 2:44ish) and you can see some clear footage of the rocker arm quite literally sloshing around oil.

Jud Chapin

1) No imagination...been changing oil in all my cars for over 50, yes 50, years and the psi change applies to all of them. BTW, it's pretty hard to "imagine" when watching the idiot light or an oil pressure gauge. I even had one of my cars, over 285k on the clock, knock for a couple of seconds when starting the engine immediately following the oil change and not doing so after the wait. Try it. My guess is you never have.

2) Incorrect...

wcsinx

What exactly is it you think the oil is doing in those 30 minutes? Working its way up into the engine without the aid of the oil pump? (see my comment about oil being subject to the same law of gravity as everything else in this universe)

Ok, then you're aware of just how long it takes to reprime an oil pump? But you're convinced this is happening everytime you change your oil?

noonie

Although I've never paid any attention, I tend to believe that's totally possible.
It probably depends on a lot of factors, akin to having a straw hold liquid with your finger over the end. (those laws of physics already mentioned)

Taking off the filter removes the finger and should allow a certain amount of the oil to drain from the oil pump. Of course it would depend on the oil and engine temp, oil viscosity and probably moreover how long you let the oil drain. I suspect you let it drain for quite a while as opposed to a Jiffy Lube oil change.

Then with the filter back on (finger on straw), when filling the pan with oil, the oil will slowly fill back into the pickup tube and pump cavity. Since the oil pump in a sbc is immersed in the oil should eventually seek the level in the pump as well.
The biggest factor in waiting, is probably that the atmospheric pressure is helping the suction side of the pump supplying fluid rather than just the air if started immediately.
The oil pump never really looses it's pumping capabilities during an oil change, there is always enough oil film on the gear end surfaces.
Difference is only if it's mostly air or oil.

Next oil changes, I'll have to take notes, just for interest's sake.

No way it would make a difference in my Ford, the pump is 3" above the pan oil level and on occasion it has knocked after an oil change.

wcsinx

I see where you're going, noonie, but do you really think that air gap in the pickup makes that much difference? You're not talking about much volume there. < 1 cup would be my guess. ...could probably achieve the same effect by simply filling completely before putting the filter back on.

Jud Chapin

I think you need to go back and read my original post. I'm done here.

noonie

Ya, I think it can make a big difference, again with the other factors involved and another perhaps the biggest, how worn the oil pump is. Don't forget it's the only moving part in the engine that uses unfiltered oil.

Time is a bigger factor than volume of oil. It may take 3 seconds for that 1 cup or 45 seconds.

Easy test, next time you want to take your pan off, note how much is in the oil pump when it's removed.
I seem to remember they're fairly empty, but as I said never paid much attention.

Not assuming anything here would double engine life, just interesting and if one has time on their hands, why not.

Glassbowtie77

I have never primed an oil filter in the 43 years that I've been driving and never had an issue. My theory is that for the relatively short time it takes to do an oil change the parts are still coated with oil and for that 2-3 seconds before the gauge pops up to pressure the parts are protected.

billcarson

Glassbowtie77 that was my thinking, so that leaves me more time to worry about being conked on the head by a meteorite.or it hitting my gal.

oldalaskaman

on big trucks, I fill them, on a gas engine for a customer , I fill them, on my own gas engine , almost never, the time between dropping the oil and filter on a gas engine, and then refilling and start up is short enough that there is still oil coating the internals that will protect it during startup, its a personal choice though, I can see the argument for always priming them especially on an older engine with increased bearing clearances
should've read post 76

LeMans Pete

I have always "primed" as a best practice. Alot of discussion and stubborn opinions over something that takes 30 seconds to do.

leadfoot4