How long does it take oil film to complete drain

[TexasTea]

Hi guys,

Just curious about a simple notion i've always been curious about..and that is, how long does it take oil to completely drain off internal components as the motor sits off, unused?

I always thought that a car that is in daily use, sitting over night, the oil or a light film, would still be coated on the internals enough to lubricate the following cold start in the morning. Is this true?

Also for motorcycles that sit for long periods of time, such as over winter season, then are started up in summer, could there still be an oil film on the internals to lubricate it? or after 4-5 months sitting would there definitely not be any oil film left on the internals (especially in the head and upper engine components) causing a more "wear-ful" startup after long periods of sitting than say, any other type of start-up?

Just curious, if there is any actual science behind this to make a educated/informed stance on the issue.

 

[HemiHawk]

Only after over night there is surely still a coating on internal parts. After a couple months? That might be a different story. If its a bike sitting for a couple of months, I'd be tempted to pull the spark wires and crank the engine, so hopefully circulate the oil a bit before actually starting. I've taken to doing this with my cars after an oil change using the "clear flood mode". Just crank the engine for a couple seconds before starting.

 

[old1]

I have also wondered the same thing with my classics. Also wondered if any type of additive or even heavier oil would leave more film than just oil? Also If it is draining pretty dry after say less than 30 days, those people that start and warm up, even drive the cars every month would have more dry starts than those of us who only start once in the spring. Also, even in the summer the classics sit for anywhere from a week to a month between runs.

 

[TexasTea]

is the clear flood mode something unique to your car or is it something you can do with other cars?

also you mentioned pulling spark plugs, should you put a few drops of oil in the cylinder thru the spark plug holes? or just pull the plugs and turn the engine over a few times?

I notice that on my small displacement motorcycles that after an oil change i can actually hear the difference at start up from oil starved and oil filled engine...and on 1 particular bike, even when filling the oil filter, there is no escaping it and it seems to leave a lasting "tick" that could've been avoided if perhaps the oil fill had been ontop of the head rather than down low by the crank case.

 

[ARCOgraphite]

Nothing to worry about in a PCMO scenario. Engines are more resilient than you think. Iso Syn and PAO will drain off immediately. Fatty esters will be there indefinitely (monolayer).

Most any oil will stay between the piston and wall and in bearing shell likely for months if not years.
Bearing journals are near mirror polished with just enough finish to hold some oil. Clearance is typ around 1 thousandth of and inch - they can spin "semi-dry" for a bit, NP.

 

[HemiHawk]

Originally Posted By: TexasTea
is the clear flood mode something unique to your car or is it something you can do with other cars?


Sorry, I should have expanded on this. Alot of modern cars have a way of cranking the engine, without starting. In the case of 2 of my manual transmission cars the process is to hold down the clutch AND gas pedal at the same time. While doing this, turn the key and the engine will turn at cranking speeds, but not start. Before trying this I would advise checking that your car has this feature, and that it wont fire up at full engine RPM floored.

Originally Posted By: TexasTea

also you mentioned pulling spark plugs, should you put a few drops of oil in the cylinder thru the spark plug holes? or just pull the plugs and turn the engine over a few times?


For this I actually mean just pulling the ignition wires, not the plugs. This will again be a way of letting you crank the engine, but not actually starting it to circulate some oil. I'm sure some one more knowledgeable than me may comment and say whether this helps anything or not, but in my mind it would as it will only run at cranking speeds so there is alot less wear going on while some oil is circulated. You bring up a good point about the couple of drops in the cylinder though, that is part of the recommended storage procedure for my smaller engines.

 

[TheExpectorate]

HemiHawk, Texas Tea - Clear Flood mode is just about universal on fuel injected cars. Simply hold the pedal down to the floor while the engine is cranking. That cuts the injection of fuel into the cylinders, meaning no fuel is injected into the cylinders. Standard procedure during a compression test. The only issue is that, with every revolution of the engine, there will either be metal parts moving against metal parts with an unknown amount of oil between, or oil coming from the oil pump. Probably more when the engine is hot and some level of oil pressure is still present.

I believe the question is somewhat flawed. An oil film is simply the oil itself. The question appears to be about oil that sticks to the parts after the engine has been shut off and the oil drains back to the pan, with gravity. That would depend more on the type of oil, as in its composition.

 

[440Magnum]

I've dug around a *lot* in salvage yards over the years. I've never yet pulled opened up an engine, even if there was a tree growing through the vehicle frame, that wasn't pretty oily inside. If someone opened it before I got there, different story. Dried oil, dirt, rust, water. But if it was a closed engine and I was the first one to look inside, it would always be oily, even if the vehicle had been there for years.

So for normal storage intervals of a few months or less, I wouldn't worry about oil film. A bigger issue is damp air getting into whichever cylinder(s) have an intake or exhaust valve open when the engine was shut down. "Fogging" the engine with a light oil into the intake just as you're shutting it down the last time of the season can help a lot with that.

 

[gregk24]

I wouldn't try clear flood mode unless you know your car has that feature. Otherwise you will be revving the mess out of a cold engine. Ask me how I know

 

[SwampSurvivor]

Me Jeep sat for about a month with the crank loosened up. Every couple of days, I would have to clean up a puddle of oil. Oil comes out of them for quite a while after they shut down. My father's truck has sat for 8 months and started right up with no funny noises - which means there was definitely oil on the stuff!

Originally Posted By: gregk24
I wouldn't try clear flood mode unless you know your car has that feature. Otherwise you will be revving the mess out of a cold engine. Ask me how I know

Did that on the first oil change on my Cherokee! I was used to Fords or even the newer Jeeps. Held the pedal to the floor and went to crank it, instantly to 4000 RPM. Built oil pressure quick, though!

After it sat for about a month with the crank loosened, I removed the spark plugs and spun it over for a minute or so to get the oil back into it.

 

[FCD]

Whenever my car sits for more than a month i pull the plugs and turn the engine over with the starter

 

[4WD]

Had several vehicles over a 25 year span that were not started for a month at a time. One I used to hunt with had a 4 bbl carb and you would have to crank on it a bit. The modern FI engines come to life so fast I don't worry about those.

 

[barryh]

When we talk of pulling the plugs to crank the engine I hope everyone realises that the ignition leads should not be left open circuit. In the absence of a gap to spark across, the the coils will get stressed by attempting to reach their maximum possible HT volts which can cause an insulation break down inside the coil. It's always good practice to put the plugs back in the ignition leads and rest them on earthed metal so they can spark during cranking.

 

[Kawiguy454]

IMO you're over thinking it. Put a drop of oil on a piece of cardboard and leave it outside. that little dot of oil will wick out as big as a vollyball and be there a month. In an enclosed engine the film will be there for years as it is really sticky. A positive displacement oil pump pressurizes the system as soon as it begins to turn so start the motor and don't rev it up or or make it do work for a bit. Ive had many motorcycles over the years and never had any wear problems due to first springtime startup.

 

[gregk24]

Originally Posted By: Miller88
Me Jeep sat for about a month with the crank loosened up. Every couple of days, I would have to clean up a puddle of oil. Oil comes out of them for quite a while after they shut down. My father's truck has sat for 8 months and started right up with no funny noises - which means there was definitely oil on the stuff!

Originally Posted By: gregk24
I wouldn't try clear flood mode unless you know your car has that feature. Otherwise you will be revving the mess out of a cold engine. Ask me how I know

Did that on the first oil change on my Cherokee! I was used to Fords or even the newer Jeeps. Held the pedal to the floor and went to crank it, instantly to 4000 RPM. Built oil pressure quick, though!

After it sat for about a month with the crank loosened, I removed the spark plugs and spun it over for a minute or so to get the oil back into it.


Same here! Tried in on my previous car, the 2006 Accord, and the tach was at 4 grand before I even had time to respond.

 

[BrocLuno]

Wow, you'all have not bee into old engines much have you? Ever torn a junk yard motor apart? There is oil everywhere, even after sitting for many months...

Old tractors sometimes sit for a year a time. No spark plug hole if they are diesel. Way to much work to pull injectors. Just hit them with a fresh battery and some starting fluid - bingo, they're running.

I beg to differ about Iso-Syn draining off. I have not witnessed that. In fact it seems to cling well (Delo400). It's still dino oil and that stuff is tenacious...

Go out with you oil can and oil apiece of steel and set it out in the sun in the back yard, not even in a closed system like a engine. That oil spot will be there and be slippery for weeks ...

In a capillary space like a bearing it all depends on surface tension. Dino oils have higher surface tension than synthetics, so they stay in small places as capillary fill better. But even synthetics will exhibit a residual oil film.

Although I have to laugh at the hot rodders who put in expensive synthetics and let the motor sit for six months between outings (and change the oil once a year with 500 miles...). Real high quality Dino oil would remain better and be entirely adequate for annual changes

That's why some motors will clatter on start-up with synthetics and not with Group II oils

 

[Lethal1ty17]

I seem to remember seeing some sort of official or semi-official study done on oil film thickness over time and how long it took to stabilize. From what I remember, about 2 hours after engine shut down, the film thickness on the cylinder walls stabilizes and from there its a quite slow decline in thickness. I can't cite it, though. Been too long and I have no idea where I saw it. So whether it is 3 hours or 3 months, the film thickness is hardly any different.

 

[FCD]

From my experience Dino oils do seem to cling better to parts when they sit, when i ran a synthetic blend after just 1 day there would be little oil coating the rockers, now with dino it's been sitting 3 days and there is still a decent coating of oil on the rockers ( Grp 1 20w50 )

 

[Shannow]

Originally Posted By: BrocLuno
Wow, you'all have not bee into old engines much have you? Ever torn a junk yard motor apart? There is oil everywhere, even after sitting for many months...


Yeah, but it's much better to "feel" that everything will be bone dry tomorrow morning, and "posit" that Japanese spec oils will flood the areas ten seconds before you think of turning the key.

 

[Silk]

I didn't even think about this when I started a motorcycle a couple of years ago that had sat for over 10 years. Oh dear, do you think I've wrecked it ? I've been riding it around since, what symptons of a destroyed engine am I looking for ?