Using super thin oil to start rebuilt engine to prevent filter bypass?

[willistheguy]

I hear about people working on engine internals and then later ruining bearings because dirt got into the oil pan, BUT, I've always wondered why the filter did not capture the debris.

Now it is my understanding that when the oil is cold, the engine's oil filter bypass can be activated because the oil is still thick. Which means any debris that got into the engine will not be filtered out until it is too late.

Is there some logic to using the thinnest oil you can get your hands on when first starting an engine that has had an overhaul so that the oil is thin enough to prevent the oil filter bypass from opening?

Now, in my personal situation, I just put a new head gasket on my 99 4.0L Jeep. It took extensive cleaning to remove the 20 year old gasket from the block surface. I used many rags to try and prevent debris from entering the lifter galley but I know some got in there. When the engine runs, the oil will drain through the galley and the debris will end up in the oil pan.

My plan: Fill the engine with 5 quarts of M1 0w20 and a new filter. Start the engine and let it run until hot. Drain the hot oil. Refill with the correct 5w30 and a new filter. Done.

I realize removing and cleaning the oil pan is probably the best way to go, maybe I'll end up doing that too, but I still want us to focus on the bold question above. Thanks.

 

[FCD]

You'll be fine just filling with a regular 5w-30, don't worry.

 

[dave1251]

I would just use a cheap 5W20 and drive for about 100 miles then change along with the filter if your worries about debris. I would not be too concerned.

 

[Astro14]

I don't know if the 0W20 will work as you intend. Oil temp on startup is one variable that would affect the answer. Interesting logic. I don't see how it would hurt, so why not give it a try?

In general, if I'm doing a cylinder head - I scrupulously avoid the use of anything abrasive. Abrasive particles in the cylinder bores, or running through the oiling system would be terrible. I scrape, with a razor blade, use a shop vac, and have very possible path for debris blocked with towels or shop rags. When done, it's cleaned with compressed air to get any debris that got past the rags. Bits of head gasket aren't that hard - I don't think they would score a cylinder wall. But carbon, bits of steel, etc. might.

How would the debris get into the oil pan? Did you have the passages blocked/plugged, too? Stuff on top of the rings/pistons is going to be on the cylinder walls until combustion blows it out.

 

[Patman]

Originally Posted by dave1251
I would just use a cheap 5W20 and drive for about 100 miles then change along with the filter if your worries about debris. I would not be too concerned.


I agree, why waste good M1 0w20 when a cheap 5w20 will do the trick?

 

[spasm3]

You did a head gasket. Since its not a complete rebuild, there is oil in the crank and oil passages and on the bearings. I would not waste m1 for a short flush. I'd prefill the filter use an inexpensive dino run it till hot an then change the oil and filter for the m1.

If you had done a compete rebuild I'd recommend filling the filter ( don't use an oversize filter here) and spin the engine over with the plugs out( This is if you can't spin the oil pump with a cut distributor shaft). Install the plugs and fire it up. then change oil.

 

[ARCOgraphite]

Put some warm 10w30 oil in there that's all.

Its MUCH MUCH thinner than a room temp 0w20.

Bigger chance You might develop a knock running incorrect grade with incorrect HTHS.

Just a footnote - If My new, solid, Nissan QE25DE engine gets a pan near 20 grade and its low HTHS, it starts mechanically knocking.

beware!

 

[53' Stude]

Originally Posted by ARCOgraphite
Put some warm 10w30 oil in there that's all.

Its MUCH MUCH thinner than a room temp 0w20.

Bigger chance You might develop a knock running incorrect grade with incorrect HTHS.

Just a footnote - If My new, solid, Nissan QE25DE engine gets a pan near 20 grade and its low HTHS, it starts mechanically knocking.

beware!


Thats the biggest load of manure you have ever blabbed

 

[dlundblad]

I just ran short OCI's (like 100 miles or so) after doing the lower intake manifold gaskets on my truck.

Despite my efforts, junk got into the engine. My first few filter runs were pretty nasty. Change it when hot obviously.. what's not caught in the filter may be suspended in the oil.

I would not use 5w20 in a 4.0.

 

[Chris142]

Dont forget to put the PH8A size filter on it. More surface so the bypass may not open as soon?

 

[oil_film_movies]

Originally Posted by willistheguy
Now it is my understanding that when the oil is cold, the engine's oil filter bypass can be activated because the oil is still thick.
At the temperature you'll be doing this at, let's assume it's 50 degF, a 5w20 or 5w30 conventional will be fine to not pop the bypass valve. I saw the worst filter at a colder 32 degF out of a group flowed 1.8 GPM at a differential pressure of 15 psi (bypass for a lot of filters) using a conventional 5w30 oil.
Your engine will probably start flowing no more than 2 gpm at start-up, and if you're at a warmer temperature in you garage or shop than 32 degF most likely, very doubtful your oil filter would go into bypass.

To be doubly sure you don't get a bypass event at startup, use a synthetic media oil filter for the least flow resistance and diff pressure, and the cheapest one that's good is a Fram Ultra at ~$9 each at walmart or amazon. Also, a 5w20, or a 5w30 mixed with a pint of SeaFoam or similar thin liquid like kerosene or diesel fuel, would be plenty thin enough to be sure.

Also, coat the cylinder walls with a very thin coat of motor oil. Before you put the head back on. Not much, just smear on some near the piston-cylinder-wall boundary.
Fill the oil filter up before installing a new one.

 

[oil_film_movies]

Originally Posted by Chris142
Dont forget to put the PH8A size filter on it. More surface so the bypass may not open as soon?
An oversize filter does reduce bypass events. An XG8A fram ultra, if that is the oversized pick, would be the best to get the lowest differential pressure at start-up.

 

[Sunnyinhollister]

If this is on a Wrangler I would just drop the pan. While I'm at it I would also do the timing chain. And use the larger oil filter.

 

[ZeeOSix]

Originally Posted by willistheguy
My plan: Fill the engine with 5 quarts of M1 0w20 and a new filter. Start the engine and let it run until hot. Drain the hot oil. Refill with the correct 5w30 and a new filter. Done


Unless you're doing the initial start-up well below zero degrees going with a thinner (0W vs 5W) oil isn't going to matter. Just don't rev the engine high until the oil warms up some. No filter is going to go into bypass at a relatively warm ambient temperature if the engine revs are low.

 

[tiger862]

I shove rags in cylinder walls and water jackets. Clean block, clean head, drain block, flush block with clean water then clean head again. Next step is remove rags from cylinder bore wipe with lint free rag then fresh oil in cylinder walls. Put together then do short OCI. Make sure tools are clean as well.

 

[SnowDrifter]

Originally Posted by oil_film_movies
Originally Posted by Chris142
Dont forget to put the PH8A size filter on it. More surface so the bypass may not open as soon?
An oversize filter does reduce bypass events. An XG8A fram ultra, if that is the oversized pick, would be the best to get the lowest differential pressure at start-up.

I disagree. The filter's bypass is based on a pressure differential over the media, which is based on viscosity, flow rate, and the media's resistance to flow. Add more media - more surface area, and there's a lower pressure delta.

As to OP, I think you're overthinking this way too hard.

Thing 1. Just because a filter goes into bypass doesn't mean it's not filtering any oil. It just means that some of it isn't being filtered.

Thing 2. Pop off the distributor and drive the oil pump with a drill for a few minutes. That'll cycle the oil through the engine, including the filter, removing the debris you're concerned about.

Thing 3. You can clean the lifter galley with some brake parts cleaner to flush everything into the pan. Make sure to follow up with a few squirts of oil. From there, it'll go through the filter before the rest of the oiling system. Just give enough time for the VOCs to evaporate before adding oil and starting the engine. If this is really a major concern for you, it might be worth your time to drop the pan and clean it, if only for peace of mind.

Thing 4. I'd be more concerned about coolant contamination in the oil than anything. Start it up for a few minutes, change oil. Start it up for another few minutes, change oil again. Done.

Thing 5. Theory vs. practice. In practice, your concerns don't appear to be reflected in the lifespan of engines that have had similar repairs done. There are many a 4.0 that's had a head gasket replaced and continue to run for thousands upon thousands of miles.

 

[DGXR]

Originally Posted by willistheguy
I hear about people working on engine internals and then later ruining bearings because dirt got into the oil pan, BUT, I've always wondered why the filter did not capture the debris.

Now it is my understanding that when the oil is cold, the engine's oil filter bypass can be activated because the oil is still thick. Which means any debris that got into the engine will not be filtered out until it is too late.

Is there some logic to using the thinnest oil you can get your hands on when first starting an engine that has had an overhaul so that the oil is thin enough to prevent the oil filter bypass from opening?

Now, in my personal situation, I just put a new head gasket on my 99 4.0L Jeep. It took extensive cleaning to remove the 20 year old gasket from the block surface. I used many rags to try and prevent debris from entering the lifter galley but I know some got in there. When the engine runs, the oil will drain through the galley and the debris will end up in the oil pan.

My plan: Fill the engine with 5 quarts of M1 0w20 and a new filter. Start the engine and let it run until hot. Drain the hot oil. Refill with the correct 5w30 and a new filter. Done.

I realize removing and cleaning the oil pan is probably the best way to go, maybe I'll end up doing that too, but I still want us to focus on the bold question above. Thanks.


Short answer: No. If you are using a thin oil to prevent filter bypass, you'd be better off using an oil filter with better flow and/or a higher bypass pressure.
On a proper rebuild: the assembly lube will protect everything until the oil pressure builds up and complete circulation throughout the oil system. The factory clearances achieved in a proper rebuild will be better lubricated by the correct oil. So use the viscosity spec'd by the engine manufacturer.

On a cylinder head/head gasket only, as another stated, the bottom end is lubricated as much as an everyday cold start. Get a quality oil filter, prime it as much as possible (depending on the base mount/orientation), and use the spec'd viscosity.

In both situations it is common practice (before the valve cover and lifter valley covers are installed) to pour a couple quarts of oil over the rockers, camshafts and lifters so that the valvetrain is lubricated as much as possible during initial start. Then install the valve cover and add the remaining oil. This is not really necessary because again the assembly lube will provide protection, but still it is common to douse everything in oil during final assembly.

Regarding your question about debris in the oil pan: Yes you will very likely get some debris flushed into the oil pan during the first run cycle. Debris small enough to make it through the oil pickup screen will be caught by the oil filter... yes the obvious exception is bypass operation, but the bottom line is you can't do anything about this except run a bypass filter. Anyway, debris large enough to be caught by the oil pickup screen usually will find its way out the drain hole at some point in the engine's life. So as long as there isn't enough debris to block the pickup screen, you're good bro. There's no way, and really no reason, to get every tiny bit of debris out of the pan without pulling and cleaning it out, which IMO is completely unnecessary. Many engines run a half-million miles on basic maintenance and never receive the level of care you are talking about.

 

[Kawiguy454]

Engine builders pull the distributor and spin the pump with a drill motor. After that doesn't the ADBV keep the passages filled with oil? so as soon as the engine begins to rotate fluid pressure begins to build. Fluid does not compress so that is very fast. A good new filter will filter a lot more capacity than the stock motor before it goes into bypass.

 

[ZeeOSix]

Originally Posted by SnowDrifter
Originally Posted by oil_film_movies
Originally Posted by Chris142
Dont forget to put the PH8A size filter on it. More surface so the bypass may not open as soon?
An oversize filter does reduce bypass events. An XG8A fram ultra, if that is the oversized pick, would be the best to get the lowest differential pressure at start-up.

I disagree. The filter's bypass is based on a pressure differential over the media, which is based on viscosity, flow rate, and the media's resistance to flow. Add more media - more surface area, and there's a lower pressure delta.


Sounds like you're all in agreement here, so why the "I disagree" statement?

 

[barryh]

If you are really that concerned about the oils viscosity at start up then pre-heating the oil would make vastly more difference than using a thinner grade of oil.