Oil Mystery, (NOT "Mystery Oil")

This post is (kind of) "just for fun", but it would be interesting to see what others say about it. I'll try to be as concise as I can. Basic oil change, nothing remarkable about it. It's the ending that's strange!

05 Tacoma. Takes 5.5 quarts of oil (with filter) for an oil change. I typically buy my oil in 5 qt and an additional 1 qt container.

$14 K&N HP 1002 K&N Premium Oil Filter: Protects your Engine: Compatible with Select FORD/LINCOLN/TOYOTA/VOLKSWAGEN Vehicle Models (See Product Description for Full List of Compatible Vehicles), HP-1002

K&N HP 1002 oil filter. Truck does NOT burn oil. Does not leak oil (noticeably). Oil level on dipstick remains constant between oil changes

Prior to oil change,
1. Dipstick, oil level is at top indicator. Engine has been sitting overnight undisturbed.
2. 5 qt container oil level is visible at the 5 qt line on the container.

Perform oil change.
1. Drain oil from engine and oil filter (Thank you Toyota for having a drain port for the oil filter!)

Replace drain plug and install new filter, add 5.5 quarts of oil

Run engine

Check dipstick (pull it, wipe it off, wait a few minutes, reinsert it and read level). Oil level is at top indicator on dipstick

HERE IS WHERE IT GETS INTERESTING:

Completely pour OLD oil from oil drain pan into empty 5 qt container used above

Oil level in 5 qt container is ALWAYS about 4 to 4.5 quarts! Shouldn't it be 5.5 quarts? Where did that "extra" quart go? If it was still in the engine the dip stick would read above the top indicator after adding new oil. Oil filter does not hold a quart of oil! Can't be there!

I've had this truck for many years, and it has always done this. Does not cause any issues, just a curiosity. Does the oil "compress" as it is being used? I would think this would change the viscosity, but hey, I'm just a backyard mechanic.

Thanks all!

TB2

 

The lubricated surface area inside the engine, from top to bottom, has a film of oil that won’t drain out in a typical oil change.

But that accumulation should be a one-time thing. It shouldn’t — couldn’t — happen every time!

Any chance the missing oil is wetting the walls of your drain pan? Any way to drain directly into one of your 5-gal jugs?

 

You always get some [say 10%] evaporation off oil. Oil tends to creep so what you are seeing may not be the exact level. Pull dipstick, wipe off, insert, read. You also are removing 1/2 quart or so with the oil filter and some stays in the engine nooks and crannies and low spots.

 

All engines burn Some oil but typically not a noticeable amount plus the filter holds around a half quart so if you figure a half quart burned over 5k and a half quart staying in the filter that would add up.

 

Hmmm, All worth considering, AND I'm not being argumentative here, but I'm not sure that little filter holds 1/2 quart. (even though an oil change with filter calls for an additional .5 qts of oil. Perhaps I'm mistaken). BUT I will say that on my oil change this morning, there was very little oil that came out of the filter! Almost as if it was dry, (which it was not and had a thin film on the inside). I've never noticed that before, but this is the first time I let it sit overnight and did not start the engine before removing the oil filter so perhaps that's normal?

And if I was evaporating .5 to 1 qt oil, my dipstick would indicate that (I would think) by showing a low or lower oil level than "full".

There is no room to drain directly into the 5 qt container. Even so, there would be a thin film of oil (which I admit may be on the walls of the engine), not .5 to 1 qt worth. The oil pan isn't that big to hold a "film" of oil that would account for it either.

5.5 quarts go in, 4-4.5 quarts come out. Filter was empty of any respectable amount of oil.

TB2

 

Cheap experiment for you: Pour a quart of oil in a pan. Now, set a new filter in it, rolling it around a few time in the next 10 minutes or so. I'll bet you'll be surprised.

 

It is in the filter.

 

In the filter, some sitting in the valleys on the heads, some in the oil pan, some in the filter. You’ll never drain out 5.5 qts.

 

The filter has aa anti-drainback valve in it to keep the oil from draining out of it and it would be really hard to notice 1/2 qt on the dipstick level.

I don't concern myself with such things, if it's in the operating range on the stick when I check it I drive it, change oil on time, and don't worry with how much comes out.

That being said it can only go 3 places, in the filter, on the ground, or out the exhaust so take your pick.

 

if you don't run the motor before changing or checking the level, it will be 'overfilled'. there's a ton of galley's and area's up top of the motor that takes hours to drain back down to the pan. you're only checking the level of the drain pan, not the level within the entire motor.

but the reason to run it before checking is to ensure that the motor has the right amount in it, as well as the right reserve amount.

 

Hmmm. Ok. All righteous answers, and worth considering, BUT... (And I'm not "arguing" with anyone or trying to be obstinate),

1. If there was a "film" of oil in the drain pan, (engine, filter...) I would doubt it would be more than a (generous) 1/3 cup or so. Far cry from 1 qt.
2. 1/2 qt in Filter? Ok IF the filter was upside down and holding 1/2 qt oil, but my filter is totally drained into the drain pan which again, leaves a film of oil in the filter. I typically unscrew it and let it drain for a few minutes into the pan before removing it. (I have a tube that goes from the filter to the drain pan). And I would think that I should yield 5 qts. and not 4.5 qts. when done.
3. Sometimes I let the engine sit overnight after driving it, oil is hot, should drain down to the bottom easily and I drain it "cold" the next morning. (Which is ambiguous in Florida summer heat! LOL!) Sometimes I drain the oil hot, always winds up the same. 4.5 qt. drained.
4. OldSchlPunk above has an interesting experiment, but I still don't think the paper in the filter holds 1/2 qt. Could be wrong. And wouldn't it depend on the brand of filter? Some are better than others.
5. If there was 1 qt oil left in the engine in pockets, film... totally drained, that implies that at factory they put in 6.5 qts. oil to achieve the correct level on the dipstick and there would always be 1 qt used old oil in the engine after oil change.
6. Each oil change yield would be increasing by 1 qt if 5.5 quarts go in, and 4.5 quarts come out each and every oil change.

If I was burning off 1 qt oil between changes, the dipstick would indicate that. Hot or cold it's always at the correct level AND I'm not burning oil, (bad rings...). No leaks, no smoke, plugs are clean. I DO concede that some oil is probably always burned off, but not a quart worth unless there are major problems.

I forgot to mention that I preform an oil change every 6000 miles, Castrol synthetic. (That remark alone will probably generate responses. LOL!)

Thanks all for your input and playing along! It's interesting to see what the responses are. I have a friend who has a Mazda and says his does the same thing!

TB2